Page 721«..1020..720721722723..730740..»

Research Fellow (Energetics of Quantum Measurement),Centre For … – Times Higher Education

About the Centre for Quantum Technologies

The Centre for Quantum Technologies (CQT) is a research centre of excellence in Singapore. It brings together physicists, computer scientists and engineers to do basic research on quantum physics and to build devices based on quantum phenomena. Experts in this new discipline of quantum technologies are applying their discoveries in computing, communications, and sensing.

CQT is hosted by the National University of Singapore and also has staff at Nanyang Technological University. With some 180 researchers and students, it offers a friendly and international work environment.

Learn more about CQT atwww.quantumlah.org

Job Description

We are searching for motivated and talented post-docs interested in the fundamental resource cost of quantum measurement and related advantages of quantum nature. The post-doc will join the Quantum Energy Team QET@Singapore led by A. Auffves.

Quantum measurement lies at the crossroad between quantum foundations and quantum technologies. One the one hand, the measurement problem has irrigated all debates about the meaning and completeness of quantum theory - On the other, measurements are key processes in quantum technologies, as they bring results at the (macroscopic) level of the end user. The present project aims to analyze the resource cost of quantum measurement and how it relates to information extraction at the quantum and classical levels. We will optimize the resulting measurement energy efficiency, with special interest in possible advantages when quantum resources are exploited to perform the measurements [1], the fact that quantum measurement can behave as an energetic resource in quantum engines [2,3], and in the intimate relation between energy cost and reversibility. The post-doc will develop theoretical concepts and models, interact with a wide network of top level experimentalists, and supervise PhD students.

Website of the Quantum Energy Team|QET>https://quantum-energy-team.cnrs.fr

Website of the quantum energy initiativehttps://quantum-energy-initiative.org

Job Requirements

More Information

For enquiries and details about the position, please contactAUFFEVES Alexia atalexia.auffeves@cnrs.fr.

Please include your consent by filling in the NUS Personal Data Consent for Job Applicants.

Employment Type: Full-time

Applications can be submitted via the link below and should contain: the latest CV, and letter of recommendation (if any).

Department: [[Centre For Quantum Technologies]]Job requisition ID: [[18794]]

Covid-19 Message

At NUS, the health and safety of our staff and students are one of our utmost priorities, and COVID-vaccination supports our commitment to ensure the safety of our community and to make NUS as safe and welcoming as possible. Many of our roles require a significant amount of physical interactions with students/staff/public members. Even for job roles that may be performed remotely, there will be instances where on-campus presence is required.

Taking into consideration the health and well-being of our staff and students and to better protect everyone in the campus, applicants are strongly encouraged to have themselves fully COVID-19 vaccinated to secure successful employment with NUS.

Here is the original post:

Research Fellow (Energetics of Quantum Measurement),Centre For ... - Times Higher Education

Read More..

Revisiting Oppenheimer and science: Its not a priesthood – Mountaintimes

By David Moats

David Moats, an author and journalist who lives in Salisbury, is a regular columnist for VTDigger. He is editorial page editor emeritus of the Rutland Herald, where he won the 2001 Pulitzer Prize for a series of editorials on Vermonts civil union law.

At a time when facts, science, and the very idea of objective truth are under assault from many quarters, its ironic that one of the big movies of the season has focused on the life of one of the most celebrated scientists of the 20th century.

That irony is not lost on Rich Wolfson, who from 1976 to 2019 was a professor of physics at Middlebury College. Wolfson appreciated that the science presented in the movie Oppenheimer was largely accurate and also that physics, his field, took center stage in the movie.

The story of J. Robert Oppenheimer deserves to be remembered. The movie is based on the book American Prometheus: The Triumph and Tragedy of J. Robert Oppenheimer by Kai Bird and Michael Sherman.

Oppenheimers most noted triumph was his success as director of the Manhattan Project during World War II, leading the effort to build the first nuclear atomic bomb. But it was a triumph that haunted him for the rest of his life because he could not look away from the fact that he had helped to create weapons capable of destroying all of humanity.

Then in 1954 his reputation came under the shadow of McCarthyite paranoia when the government revoked his security clearance after a campaign of character assassination had raised specious questions about his patriotism.

The Oppenheimer story resonates with Rich Wolfson in part because Wolfsons work as a physicist has led him to try to shed light on the benefits and dangers of nuclear technology. He is the author of a book called Nuclear Choices for the Twenty-First Century: A Citizens Guide, written with co-author Ferenc Dalnoki-Veress. It is a primer on various useful and/or dangerous forms of nuclear technology, including nuclear medicine, nuclear power generation and waste, and nuclear weapons. The book is meant to provide a basic understanding of the questions confronting the public in these complex areas of public policy.

Oppenheimers work as a scientist placed him in that elite priesthood of physicists developing an understanding of quantum theory and the mysterious properties of the atom. Wolfson has labored over the years to make the baffling realities of modern physics accessible to those beyond that priesthood to the nonscientific lay public.

Toward that end he is the author also of a widely used physics text and of a book called Simply Einstein, which seeks to explain Einsteins theory of relativity in a way that is comprehensible to the nonscientist. And he has produced a series of 24 half-hour video lectures explaining Einsteins theory of relativity and quantum theory to a nonscientist audience. (They are available on YouTube fromThe Great Courses.)

Both the book and the videos require close attention, but they succeed in showing that Einsteins theory was based on common-sense, if counterintuitive, observations that make sense when carefully explained.

Oppenheimer was conscious of the fact that science existed within a broader culture and was, in fact, an important force in shaping modern culture. This was evident in a lecture he delivered in 1965 a lecture, it turns out, where I happened to be in the audience.

I had a vague memory that Oppenheimer had delivered an address at the University of California at Santa Barbara when I was there. I remembered little about it and wasnt sure it had actually occurred. I could find no mention of the event online, but the public affairs office at UCSB managed to track down a tape of the speech in the university library. At my request, the library forwarded to me an audio file of the speech, which Oppenheimer had delivered for the university convocation of October 1965.

At his home in Middlebury, Wolfson and I listened to Oppenheimer at the lectern in California 58 years ago. It was a learned, thoughtful speech, ranging over the history of science from ancient Greece to Isaac Newton to Darwin and up to that day in 1965, with fleeting reference to the ultimate danger represented by nuclear weapons.

It was so learned that Wolfson wondered if a contemporary audience could sit still for it, or if after five minutes they would be fidgeting with their phones. In 1965, Oppenheimer earned enthusiastic and prolonged applause.

Before science became a force in human culture, Oppenheimer suggested, culture mainly served to stop change, to defend what he called the eternal verities. But after Galileo, Newton and the scientific advances that followed, science became an agent of change that was irreversible. What brought about the scientific revolution, Oppenheimer said, was an idea of progress and the idea that the betterment of mans condition has meaning.

Science grows out of common sense, curiosity, observation, and reflection, Oppenheimer said. It was an immense job to teach the complex lessons of science, but he said that science was not merely a quantitative endeavor. It involves a quest for harmony, elegance, and beauty, he said. We hunger for nobility.

If a belief in objective truth has come under siege in contemporary America, Oppenheimer had a rejoinder in his understanding of the laws of physics. He said that if alien beings were studying physics on a distant planet, they might not find the same answers as humans have found, but that would be because they were asking different questions. If they were asking the same questions, they would get the same answers. The laws of physics pertain everywhere.

After hearing Oppenheimers 1965 lecture, Wolfson said that science need not be a priesthood. It is still tied to everyday experience, he said. A huge portion of everyday experience can be explained by Newtonian science.

That science is woven into the fabric of society is evident everywhere from the science that developed the computers on which this story is appearing, to the vaccines that have kept millions of people alive, not just through Covid, but through epidemics as varied as smallpox, measles and polio.

Wolfson quoted a former senator from Oklahoma, James Inhofe, who asserted that his opinion was as good as any science. It turns out that in the face of recent climate-related disasters, Inhofes opinions about climate change have proven to be irrelevant, except insofar as they have retarded action addressing the crisis. The laws of physics do not concern themselves with the opinions of an Oklahoman with a political agenda.

In fact, the inconvenient truths of climate change have been before us for decades. We look away at our peril.

Thus, Wolfsons focus in recent years has shifted away from the nuclear danger to the reality of climate change. It is an apt topic for a physicist.

Climate is all about energy, he said.

On that topic, as on others, Oppenheimer had good advice 58 years ago. We need to reknit the discourse and understanding between us, he said. We have to learn to talk to one another. And we have to hear.

Link:

Revisiting Oppenheimer and science: Its not a priesthood - Mountaintimes

Read More..

Physics at Imperial College London: What it’s like to be part of a … – Study International News

Be part of a diverse community of pioneers, creators and innovators at the UKs third-ranked university for physics and astronomy. Join Physics at Imperial College London today.

As one of the largest physics departments division in the UK with an outstanding reputation for excellence in research, the Department of Physics at Imperial College London is where youll be able to find answers to some of the biggest questions of our universe and reality. Indeed, the department offers more than education, unlocking a world of inquiry to its students and inviting more to step into the forefront of scientific exploration.

Italian-French student Stella found just that here. Always seeking to understand the complexities of the universe, it was an obvious choice for her to join a department that was home to several Nobel Prize in Physics winners. Cutting-edge research and distinguished scientists aside, Stella was also drawn to the idea of specialising in theoretical physics while also delving into fields like philosophy and political philosophy.

The Physics with Theoretical Physics MSci programme aligned with her goals perfectly.The professionally accredited degree, which includes an integrated year of masters level study, lets Stella tailor her studies to suit her interests and aspirations across a range of optional modules. After building an excellent grounding in a range of physics, mathematics and experimental methods, the programme gives students the opportunity to specialise across a variety of topics including cosmology, laser technology and quantum physics.

Those nervous about beginning a rigorous course at a world-leading university can take comfort in knowing it didnt take long for Stella to feel at home, within and beyond campus.

To me, London is not a city of the world, but rather, the world in a city! she enthuses. Furthermore, the Imperial community is incredibly diverse, international and open. Hence, whoever you are, where you come from and whatever drives you, you will find your place! I certainly did.

Immersed and engaged at the seventh most international university in the world, the student was able to whole-heartedly work toward developing the skills and knowledge needed to pursue her dream career in research. The department was no passive observer in this pursuit. It encourages all students to be active members of its research community. Stella seized the opportunity to explore the cosmos through the Undergraduate Research Opportunities Programme, focusing on cosmology and astrophysics within a theory group. Another project is already on the horizon.

Getting hands-on experience doing research and learning from like-minded researchers and professors in your field of interest is a great asset when it comes to kick-starting a career in research, she says.

For graduate Sofa a, her Imperial journey was just as horizon-broadening. Through the International Research Opportunities Programme, she had the chance to spend a summer in China exploring 5G at Tsinghua University. It opened my eyes to see that I didnt have to stay in Europe I could explore other places in the future and see how things are done differently, she says. It was an extremely positive experience.

Such opportunities make it all the easier for MSci students to get a better understanding of the areas of focus that matter the most to them. Many dive deeper into these topics during their fourth-year research project. For example, Kantaphat Pinaree further explored the exoplanet by investigating the atmospheric composition of the hot gas giant WASP-69b. Anthea MacIntosh-LaRocque focused on building a detector to map a proton beams dose profile and ultimately fight cancer with physics. Nadia Cooper looked into the interplay between gravity, quantum theory, and extreme conditions, focusing on the behaviour of charged black holes.

The BSc Physics provides access to state-of-the-art laboratories and top-of-the-line research resources, too. This three-year programme which can be followed up with a one-year postgraduate MSc course is a better fit for students looking to lay a solid foundation by developing the numerical, logical thinking and problem-solving skills required to impress the employers of both today and tomorrow.

All programmes are delivered from the heart of London, the global academic capital. Regardless of their background, everyone discovers something special in this multicultural, vibrant city. For StellaCloz, studying in the heart of South Kensington, a stones throw away from the serenity of Hyde Park and close iconic landmarks and museums, has been nothing short of a blessing. Its artistic and musical scenes, always lively, youthful, and intriguing, have never failed to energise her.

Be careful, though, she says. Once you leave London, you will find yourself missing and longing to come back.

Follow Imperial College London on Facebook, Instagram, X, YouTube, and LinkedIn

See the rest here:

Physics at Imperial College London: What it's like to be part of a ... - Study International News

Read More..

New telescopes to study the aftermath of the Big Bang – Phys.org

This article has been reviewed according to ScienceX's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility:

fact-checked

trusted source

proofread

close

Astronomers are currently pushing the frontiers of astronomy. At this very moment, observatories like the James Webb Space Telescope (JWST) are visualizing the earliest stars and galaxies in the universe, which formed during a period known as the "Cosmic Dark Ages." This period was previously inaccessible to telescopes because the universe was permeated by clouds of neutral hydrogen.

As a result, the only light is visible today as relic radiation from the Big Bangthe cosmic microwave background (CMB)or as the 21 cm spectral line created by the reionization of hydrogen (aka the Hydrogen Line).

Now that the veil of the Dark Ages is being slowly pulled away, scientists are contemplating the next frontier in astronomy and cosmology by observing "primordial gravitational waves" created by the Big Bang. In recent news, it was announced that the National Science Foundation (NSF) had awarded $3.7 million to the University of Chicago, the first part of a grant that could reach up to $21.4 million. The purpose of this grant is to fund the development of next-generation telescopes that will map the CMB and the gravitational waves created in the immediate aftermath of the Big Bang.

Gravitational waves (GW), originally predicted by Einstein's theory of general relativity, are ripples in spacetime caused by the merger of massive objectslike black holes and neutron stars. Scientists have also theorized that there are GWs formed during the Big Bang that could still be visible today as vibrations in the background. In collaboration with the Lawrence Berkeley National Laboratory (LBNL), researchers from the CMB-S4 project University of Chicago seek to build telescopes and infrastructure in Antarctica and Chile to search for these waves.

The collaboration currently involves 450 scientists from more than 100 institutions in 20 countries. The entire project is proposed to be jointly funded by the NSG and the U.S. Department of Energy (DoE), with the NSF's portion being led by the University of Chicago, while Lawrence Berkeley National Laboratory will lead the DoE portion. The project is expected to cost a total of about $800 million and become operational by the early 2030s. In addition to searching for primordial GWs, these telescopes could also map the CMB in incredible detail and reveal how the universe has changed over time.

These telescopes could also help search for the elusive "dark universe" and validate our current cosmological models. John Carlstrom is the Subrahmanyan Chandrasekhar Distinguished Service Professor of Astronomy and Astrophysics and Physics at UChicago and the project scientist for CMB-S4. "With these telescopes, we will be testing our theory of how our entire universe came to be, but also looking at physics at the most extreme scales in a way we simply cannot do with particle physics experiments on Earth," he said in a UChicago News statement.

Because the CMB carries information about the birth of the universe, scientists have been mapping it for decades. These include space-based telescopes like the Soviet RELIKT-1, NASA's Cosmic Background Explorer (COBE), the Wilkinson Microwave Anisotropy Probe (WMAP), and the ESA's Planck satellite. These missions have measured small temperature anisotropies (fluctuation) in the CMB with increasing detail, providing hints about how the universe began. What is needed, however, are telescopes sensitive enough to answer the deeper cosmological questions, like whether the universe began with a burst of inflation.

To this end, the CMB-S4 will build incredibly complex instruments to map the first light of the universe from spacecraft and the ground. The array will include two new telescopes in the Chilean Atacama Plateau and nine smaller ones at the NSF's South Pole Station (SPS). The project will also rely on the South Pole Telescope, which has been operational at the SPS since 2007. Each site will play an essential role, with the telescopes in Chile conducting a wide survey of the sky to capture a more detailed picture of the CMB. Meanwhile, the telescopes at the NSF's South Pole Station would take a deep, continuous look at a smaller part of the sky.

The observations from Chile will help improve our understanding of the evolution and distribution of matter and look for relic light particles that may have existed in the early universe. Meanwhile, the telescopes in Antarctica will offer a unique look at the universe since it is here that the rest of the Earth spins around, permitting continuous observations of one section of the sky. Their combined efforts will allow astronomers to look for the ripples in spacetime that could only emerge from a space smaller than a subatomic particle suddenly expanding into a much larger volume.

Said Lawrence Berkeley National Laboratory physicist Jim Strait (the project director for CMB-S4), this is an ambitious but worthwhile goal. "In many ways, the theory of inflation looks good, but most of the experimental evidence is somewhat circumstantial," he said. "Finding primordial gravitational waves would be what some people have called 'the smoking gun' for inflation."

Since these ripples would interact with the CMB and leave a distinct (but extremely faint) signature, large-scale and continuous mapping of the CMB should provide indications of their existence. The CMB-S4 should also provide clues about the nature of dark matter and dark energy. Whereas the former is theorized to account for the majority of the mass in the universe (about 69%), the latter is responsible for its accelerating rate of expansion. Furthermore, mapping primordial gravitational waves would also help scientists find the connection between the forces of gravity and quantum mechanics.

Microwave detectors are already so sensitive that measurements are dominated by background noise and local interference. Therefore, the plan is to outfit the combined CMB-S4 experiment with nearly 500,000 superconducting detectors, more than all previous experiments combined, and to greatly increase the number of measurements to provide a precise measurement of the signal level and reduce the noise. The new grant from the NSF will help fund the design of the new telescopes and site infrastructure, which will be the most complex ever built.

More:

New telescopes to study the aftermath of the Big Bang - Phys.org

Read More..

Quantum Computers Explained. The Quantum Leap … – Medium

Quantum computers

Quantum technology

What on earth is a quantum computer?

Bits! Qubits!

Try all the codes at once!

Whichever nation first develops a practical quantum computer will have a tremendous advantage

Quantum Supremacy

The world is abuzz with talk of quantum computers, but the information can be muddled and confusing, and sometimes downright incorrect.

Quantum computers arent simply super-sized versions of our current computers; theyre something entirely different, and that difference is the key to understanding their monumental significance.

Imagine stepping into a world where computers are no longer bound by the limitations of classical computing, where machines can solve complex problems that were once thought impossible, and where the very fabric of reality is harnessed to transform technology as we know it. Welcome to the world of quantum computing, a realm that is set to revolutionize not only the way we compute but also how we understand the universe itself.

Bits! Qubits! If these words sound like gibberish to you, fear not; youre not alone. Quantum computers, often touted as the future of computing, are shrouded in an enigmatic aura. Lets demystify them.

At first glance, a quantum computer might appear much like your ordinary computer. Quantum computers, often misunderstood as just bigger, faster versions of classical computers, are, in fact, something entirely different.

However, beneath its unassuming exterior lies a complex web of qubits, the building blocks of quantum computation.

They operate on the principles of quantum physics, featuring qubits as their building blocks. Unlike classical bits, which can only represent 0 or 1, qubits exist in a superposition of states, a feature that forms the core of quantum computings incredible power. Its like juggling multiple balls at once, with each ball representing a different possibility.

Originally posted here:

Quantum Computers Explained. The Quantum Leap ... - Medium

Read More..

How can queering research methods improve physics education? – Astrobites

Title: Queering methodologies in physics education research

Author: Madison Swirtz (they/them) and Ramn Barthelemy (he/him)

First Authors Institution: University of Utah, Salt Lake City

Status: Presented at Physics Education Research Conference 2022 [open access]

Physics education research (PER) is the study of how physics is taught and how to make its teaching effective for all physics students. A lot of this research involves either quantitative, i.e. counting statistics from surveys, or qualitative work, i.e. interviewing participants about their experiences. With more and more people looking into how to make physics education more equitable, diverse, and inclusive, recent research has focussed on studying underrepresented groups experiences in physics learning environments. But are the questions we are asking in PER the right questions we really need to make physics education better for minoritised students? Todays paper looks at how ideas from queer theory can be used in PER to improve the reality of physics education.

The paper defines to queer as:

to make strange, to frustrate, to counteract, to delegitimize, to camp up heteronormative knowledges and institutions.

In other words, queering encompasses both the definitions of the unexpected and non-conforming, and of resisting societys traditional ideas about gender or sexuality. Queering research methods specifically means breaking into (and apart) the approach to a research question: as being queer is existing and thinking outside mainstream heteronormative society, queering research methods means approaching a research problem from a completely different angle. Additionally, queer methods look at deconstructing how research methods yield to the heteronormative status quo prevailing in institutional academia.

This definition highlights some of the contradictions between queer theory and current methods in PER:

To count is to agree that there is a well-bounded definition.

Lived identities and experiences are often obscure and nebulous, and its hard to create finite categories to encompass all identities. How do you count everyone in a survey without leaving someone out and diminishing their experience?

To summarise and analyse is to impose your own values onto your research participants.

Understanding results from studies often requires relating these back to the perspective of the researcher. How can we empower the participants of PER studies?

To report on your findings is an attempt to assimilate yourself into the heteronormative culture of the academy.

When dealing with funding sources and institutional goals, how can researchers resist institutional status quo? How much of the structure of the academy can truly be changed to help minoritised students?

This doesnt just have to relate to research methods in PER, the paper also highlights how special relativity has queered kinematics by requiring a reconceptualisation of physics as it was known previously. Playing around, making physics strange, twisting and breaking it apart has revolutionised modern physics. Queering physics is essential for understanding our universe.

Some quantitative research can have a positive impact on diversity issues, for example a survey of the demographics of introductory physics students found that these students did not fit typically assumed categories of white men learning calculus-based physics at high-ranking universities. However, qualitative research can also cause trouble when assigning participants into categories. For example, non-binary people are often overlooked in surveys only referring to binary gender.

In queer theory, gender can be better understood as a wider combination of peoples experiences. Quantitative studies can reduce a persons whole experience to one dimension, leaving out the important intersection between identities such as how race and gender combined affect a persons experience in STEM spaces. Todays paper quotes an example of how nerd culture is often associated with a certain image restricted to white and Asian men, while it is gatekept from people who dont fit that stereotype. These are the types of identities that typical surveys do not consider but that a queer research framework can highlight.

Additionally, because physics environments are overwhelmingly male, white, heterosexual, and cisgender, a survey that averages over all identities other than gender will be biased towards white, heterosexual, and cisgender populations. This quantitative research would then, when looking at the experience of a woman in physics, result in only understanding the experience of cisgender straight white women. This leaves women of colour and transgender womens experiences unaccounted for when suggesting improvements to make in physics education.

The paper makes some suggestions that quantitative surveys need to consider: make sure surveys dont reinforce binary categories and allow self-identification so no-one is excluded; the methods should be chosen based on research goals; and the pool of participants should be sufficiently diverse and include gender non-conforming participants. In general, just as should be done in other areas of physics and astronomy research, queering quantitative research means questioning the limitations and the assumptions of the data you are studying.

In terms of qualitative research, the paper outlines some innovative research methods from previous studies. These methods particularly emphasise the effectiveness of empowering participants and giving them more control of their story, opening up the walls beyond question and response into something more expressive and personal.

These methods include basing research off of the researchers personal experiences in a reflective autoethnography, and inviting queer students of colour to photograph the places, people, and things that made them feel a sense of belonging. Other studies hold pre-interviews with participants so that the participants can understand the researchers goals, methods, and biases, while the researcher can learn to improve their own study.

Breaking down the researcher/participant binary in turn allows breaking down of power structures, allows for more honesty in qualitative research, and adds richness and complexity to these studies. The creative approach of making qualitative research fun for participants will hopefully give a new level of understanding to how students enjoy learning in physics, in turn pointing out the next improvements to make to physics education.

The paper introduces queering methods as something paradoxical; methods which are rigid, well defined, and require conformity cause tension with the definition of queering, seemingly the opposite, undefined, fluid and expansive. But when thinking of queering methods as breaking apart existing methods and exposing contradictions, new innovative discoveries can grow from these paradoxes, just like special relativity from kinematics. The queer contradiction continues in modern physics with the paradox between quantum mechanics and general relativity. Working with these contradictions both in queering physics education and queering physics concepts will pioneer the road for future research and for the experiences of future researchers.

Astrobite edited by Yoni Brande

Featured Image Credit: Art by Storm Colloms

About Storm CollomsStorm is a postgraduate researcher at the University of Glasgow, Scotland. They work on understanding populations of binary black holes and neutron stars from the gravitational wave signals emitted when they merge, and what that tells us about the lives and deaths of massive stars. Outwith astrophysics they spend their time taking digital and film photos, and making fun doodles of their research.

Here is the original post:

How can queering research methods improve physics education? - Astrobites

Read More..

Breaking the Quantum Limit: From Einstein-Bohr Debates to … – SciTechDaily

In the Barz groups experiment with a two-stage interferometer auxiliary photons are used to generate distinct measurement patterns for all four Bell states, increasing the efficiency beyond the traditional limit of 50%. Credit: Jon Heras, Cambridge Illustrators

Researchers at the University of Stuttgart have demonstrated that a key ingredient for many quantum computation and communication schemes can be performed with an efficiency that exceeds the commonly assumed upper theoretical limit thereby opening up new perspectives for a wide range of photonic quantum technologies.

Quantum science not only has revolutionized our understanding of nature, but is also inspiring groundbreaking new computing, communication, and sensor devices. Exploiting quantum effects in such quantum technologies typically requires a combination of deep insight into the underlying quantum-physical principles, systematic methodological advances, and clever engineering. And it is precisely this combination that researchers in the group of Prof. Stefanie Barz at the University of Stuttgart and the Center for Integrated Quantum Science and Technology (IQST) have delivered in recent study, in which they have improved the efficiency of an essential building block of many quantum devices beyond a seemingly inherent limit.

One of the protagonists in the field of quantum technologies is a property known as quantum entanglement. The first step in the development of this concept involved a passionate debate between Albert Einstein and Niels Bohr. In a nutshell, their argument was about how information can be shared across several quantum systems. Importantly, this can happen in ways that have no analog in classical physics.

The discussion that Einstein and Bohr started remained largely philosophical until the 1960s, when the physicist John Stewart Bell devised a way to resolve the disagreement experimentally. Bells framework was first explored in experiments with photons, the quanta of light. Three pioneers in this field Alain Aspect, John Clauser, and Anton Zeilinger were jointly awarded last years Nobel Prize in Physics for their groundbreaking works toward quantum technologies.

Bell himself died in 1990, but his name is immortalized not least in the so-called Bell states. These describe the quantum states of two particles that are as strongly entangled as is possible. There are four Bell states in all, and Bell-state measurements which determine which of the four states a quantum system is in are an essential tool for putting quantum entanglement to practical use. Perhaps most famously, Bell-state measurements are the central component in quantum teleportation, which in turn makes most quantum communication and quantum computation possible.

The experimental setup consists exclusively of so-called linear components, such as mirrors, beam splitters, and waveplates, which ensures scalability. Credit: La Rici Photography

But there is a problem: when experiments are performed using conventional optical elements, such as mirrors, beam splitters, and waveplates, then two of the four Bell states have identical experimental signatures and are therefore indistinguishable from each other. This means that the overall probability of success (and thus the success rate of, say, a quantum-teleportation experiment) is inherently limited to 50 percent if only such linear optical components are used. Or is it?

This is where the work of the Barz group comes in. As they recently reported in the journal Science Advances, doctoral researchers Matthias Bayerbach and Simone DAurelio carried out Bell-state measurements in which they achieved a success rate of 57.9 percent. But how did they reach an efficiency that should have been unattainable with the tools available?

Their outstanding result was made possible by using two additional photons in tandem with the entangled photon pair. It has been known in theory that such auxiliary photons offer a way to perform Bell-state measurements with an efficiency beyond 50 percent. However, experimental realization has remained elusive. One reason for this is that sophisticated detectors are needed that resolve the number of photons impinging on them.

Bayerbach and DAurelio overcame this challenge by using 48 single-photon detectors operating in near-perfect synchrony to detect the precise states of up to four photons arriving at the detector array. With this capability, the team was able to detect distinct photon-number distributions for each Bell state albeit with some overlap for the two originally indistinguishable states, which is why the efficiency could not exceed 62.5 percent, even in theory. But the 50-percent barrier has been busted. Furthermore, the probability of success can, in principle, be arbitrarily close to 100 percent, at the cost of having to add a higher number of ancilla photons.

Also, the most sophisticated experiment is plagued by imperfections, and this reality has to be taken into account when analyzing the data and predicting how the technique would work for larger systems. The Stuttgart researchers therefore teamed up with Prof. Dr. Peter van Loock, a theorist at the Johannes Gutenberg University in Mainz and one of the architects of the ancilla-assisted Bell-state measurement scheme. Van Loock and Barz are both members of the BMBF-funded PhotonQ collaboration, which brings together academic and industrial partners from across Germany working towards the realization of a specific type of photonic quantum computer. The improved Bell-state measurement scheme is now one of the first fruits of this collaborative endeavor.

Although the increase in efficiency from 50 to 57.9 percent may seem modest, it provides an enormous advantage in scenarios where a number of sequential measurements need to be made, for example in long-distance quantum communication. For such upscaling, it is essential that the linear-optics platform has a relatively low instrumental complexity compared to other approaches.

Methods such as those now established by the Barz group extend our toolset to make good use of quantum entanglement in practice opportunities that are being explored extensively within the local quantum community in Stuttgart and in Baden-Wrttemberg, under the umbrella of initiatives such as the long-standing research partnership IQST and the recently inaugurated network QuantumBW.

Reference: Bell-state measurement exceeding 50% success probability with linear optics by Matthias J. Bayerbach, Simone E. DAurelio, Peter van Loock and Stefanie Barz, 9 August 2023, Science Advances.DOI: 10.1126/sciadv.adf4080

The work was supported by the Carl Zeiss Foundation, the Centre for Integrated Quantum Science and Technology (IQST), the German Research Foundation (DFG), the Federal Ministry of Education and Research (BMBF, projects SiSiQ and PhotonQ), and the Federal Ministry for Economic Affairs and Climate Action (BMWK, project PlanQK).

The rest is here:

Breaking the Quantum Limit: From Einstein-Bohr Debates to ... - SciTechDaily

Read More..

A deep look into the dipolar quantum world – Phys.org

This article has been reviewed according to ScienceX's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility:

fact-checked

peer-reviewed publication

trusted source

proofread

close

In a new collaboration, two research groups, one led by Francesca Ferlaino and one by Markus Greiner, have joined force to develop an advanced quantum gas microscope for magnetic quantum matter. This state-of-the-art instrument reveals intricate dipolar quantum phases shaped by the interactions as reported in Nature.

Magnetic atoms are central to Ferlaino's research on unexplored quantum matter. At both the Institute of Quantum Optics and Quantum Information (IQOQI) of the Austrian Academy of Sciences and the Department of Experimental Physics at the University of Innsbruck, the experimental physicist and her team achieved the first Bose-Einstein condensate of erbium in 2012. In 2019, she led one of the teams observing for the first time supersolid states in ultracold quantum gases of magnetic atoms.

At Harvard University, German experimental physicist Markus Greiner is the pioneer of optical techniques allowing for the direct observation of individual atoms. Using high-resolution microscopy, the Harvard team has unveiled many exotic phenomena in strongly correlated ultracold atoms, as anti-ferromagnetic phases in 2017.

A few years ago, Ferlaino and Greiner combined their expertise to construct a quantum gas microscope tailored for magnetic atoms, aiming to access yet new phenomena. "Owing to their pronounced magnetic nature, these particles exert influence over greater distances compared to their non-magnetic counterparts, and their effects are consistently directional," Ferlaino notes. "The unique properties of these particles open up interaction regime in quantum gases unobservable in traditional experiments, granting fresh perspectives on solid-state behavior."

The research teams collaborated for years to develop and build two new experiments, one in Austria and one in the U.S. Presently, both Harvard and Innsbruck are equipped with quantum gas microscopes tailored for dipolar quantum gases.

This technology is combined with laser beams to create a light crystal where erbium atoms, cooled to near absolute zero, nest. Magnetic fields reorient these particles, providing control over their long-range, dipolar interactions. With the microscope's lens nested within the glass vacuum cell, the entire arrangement evokes the imagery of a ship inside a bottle.

In Nature, Greiner's group now presents the first results of experimental work on the new platform. The researchers have demonstrated the ability to produce varied dipolar quantum solids from superfluid phases by adjusting the interactions between particles. Distinct patterns manifest in the microscope, ranging from stripes and checkerboards to diagonal lines. "In this context, the long-range dipolar interactions among particles determine the phase of the quantum matter, with the light crystal's organizing power being broken," says Ferlaino.

At the heart of this breakthrough was many years of close collaboration between two experimental research groups across an ocean. The joint work now facilitates simulations of quantum systems with long-range, dipolar interactions, laying the groundwork for a novel understanding of quantum matter. "Such simulations offer intriguing perspectives on phenomena governed by these interactions, like ferromagnetism," notes Ferlaino.

More information: Lin Su et al, Dipolar quantum solids emerging in a Hubbard quantum simulator, Nature (2023). DOI: 10.1038/s41586-023-06614-3

Maximilian Sohmen et al, A ship-in-a-bottle quantum gas microscope for magnetic mixtures, arXiv (2023). DOI: 10.48550/arxiv.2306.05404

Journal information: Nature , arXiv

Read the rest here:

A deep look into the dipolar quantum world - Phys.org

Read More..

Distorted crystals: A revolution in 6G, quantum gravity research – IndiaTimes

NEW DELHI: A new type of crystal has been found to manipulate light in a manner reminiscent of the gravitational forces exerted by black holes. This phenomenon, termed "pseudogravity," opens the door to potential applications in 6G communication technology and offers new possibilities for exploring quantum gravity, reported Space.com The findings of this study were recently published in the prestigious journal Physical Review A.The research team, led by Kyoko Kitamura, a professor in the graduate school of engineering at Tohoku University in Japan, embarked on this study by working with photonic crystals which are crystals with a regular, grid-like structure composed of two or more arrangements, capable of slowing down the speed of light passing through them. The team initiated their experimentation by deliberately distorting these photonic crystals, disrupting their crystalline lattice, and then directed beams of light through the crystals, closely monitoring the light's deflection.Kitamura elaborated on the significance of their findings, explaining, "Much like gravity bends the trajectory of objects, we came up with a means to bend light within certain materials."The ability to manipulate light in this manner offers a potential pathway for the development of next-generation communication technology, specifically for 6G networks. These networks demand the transmission of information wirelessly at ultrahigh speeds, operating in the terahertz range (above 100 gigahertz). This is a significant leap beyond the capabilities of current 5G technology, which maxes out at 71 gigahertz. Researchers anticipate that creative manipulation of light is a key approach to achieving these frequencies, thereby revolutionising wireless communication.The applications of this newfound crystal are not limited to telecommunications. Study co-author Masayuki Fujita, an associate professor at Osaka University in Japan, highlighted the academic significance of the research. He said that these photonic crystals could potentially harness gravitational effects, opening up fresh opportunities within the field of graviton physics.Gravitons, hypothetical quantum particles that mediate the force of gravity, remain elusive to observation. Scientists have yet to fully conceptualise the properties and characteristics of these theoretical particles. Nonetheless, this research takes a step toward unravelling the mysteries of quantum gravity, potentially uniting quantum mechanics with Albert Einstein's theory of relativity.

Follow this link:

Distorted crystals: A revolution in 6G, quantum gravity research - IndiaTimes

Read More..

Scientists demonstrate the existence of a universal lower bound on topological entanglement entropy – Phys.org

This article has been reviewed according to ScienceX's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility:

fact-checked

peer-reviewed publication

trusted source

proofread

by Tejasri Gururaj , Phys.org

close

In a new study, scientists from the US and Taiwan have theoretically demonstrated the existence of a universal lower bound on topological entanglement entropy, which is always non-negative. The findings are published in the journal Physical Review Letters.

Quantum systems are bizarre and follow their own rules, with quantum states telling us everything we know about that system. Topological entanglement entropy (TEE) is a measure that provides insights into emergent non-local phenomena and entanglement in quantum systems with topological properties.

Given the fundamental role of quantum entanglement in quantum computing and various information applications, understanding TEE becomes essential for gaining insights into the behavior of quantum systems.

In quantum systems, it's often observed that the entanglement entropies follow an area law. This means that the entanglement between particles or regions is related to the area of the boundary that separates them. TEE is a specific term within the entanglement entropy that provides additional information. It's like a correction term that characterizes the topological phase of the system.

In condensed matter physics, a topological phase refers to a specific state of matter characterized by unique topological properties. These properties are associated with the behavior of particles within the material, such as anyons, and can be distinguished by their TEE values.

"TEE is a fascinating thing. By computing the entanglement entropy from a single ground state, we can learn the number of species of anyons (emergent particles that are neither boson nor fermion) of the phase of matter. It came out 18 years ago. I believe many people got inspiration from it. The research area I work on may not exist without these early works," Dr. Bowen Shi, lead author of the study, told Phys.org.

In many models, TEE is thought to have a universal value that characterizes the properties of the underlying topological phase. However, this is not always the case. TEE can differ between two states that are related by constant-depth circuits. These circuits are a specific type of quantum circuit operation that performs a series of quantum gates or transformations in a way that restricts their depth, meaning the number of sequential operations.

The key idea is that these circuits manipulate quantum states, and according to the theory, states related by such circuits should be in the same phase because the operations don't significantly alter the underlying physics.

However, this isn't always the case, and the variations in TEE between such states are often referred to as spurious TEE.

Dr. Shi underscores the transformative power of TEE, saying, "The first time I read the original TEE papers, I was in graduate school studying particle physics. Now, I study emergent particles, where certain properties naturally emerge with large degrees of freedom. My collaborators and I argued that we can now use a single wave function and the entanglement area law to predict the emergence of anyons and the correct TEE value."

Essentially, they have a tool for understanding and predicting the behavior of emergent particles and their entanglement characteristics.

The researchers wanted to understand the reliability of extracting universal properties from a ground-state wave function. To explore this, they focused on two-dimensional (2D) gapped ground states.

These states exist in 2D systems, such as thin films or 2D materials, and are characterized by an energy gap that separates the ground state from higher-energy excited states. This energy gap ensures the stability and well-defined nature of the ground state, making it an ideal platform for investigating TEE.

Following this, they introduced noise to the gapped ground states using a constant-depth circuit. This noise is akin to perturbations or disturbances in the system. They aimed to observe how the spurious TEE changed when the gapped ground state was perturbed. What they found was truly remarkable.

"We found that the new state must extract a larger value of TEE than the state without noise. In other words, the so-called spurious topological entanglement entropy is always non-negative," explained Dr. Shi.

This basically means there is a universal lower bound on TEE, which is consistently non-negative. In simple terms, the entanglement entropy within these 2D gapped ground states remains non-negative, regardless of the perturbations introduced by the constant-depth circuit.

Dr. Shi compared this to a glass being always lighter once we wipe away the dust on its surface. Wiping away dust from a glass doesn't make it heavier but rather reveals its true weight. Similarly, adding noise doesn't decrease the TEE but reveals an additional, non-negative TEE in the system.

Furthermore, the researchers made an important observation: TEE is invariant under constant-depth quantum circuits. This makes it a useful tool for understanding the underlying topological phase of the ground state.

Speaking of the potential practical implications of their research, Dr. Shi said, "TEE computation is essential for identifying a material's underlying phase. Previous studies revealed that TEE formula failure in noisy states introduced uncertainty in results. Our lower bound reduces half of this uncertainty, offering practical value. With the rise of quantum computing and preparation of quantum states, our findings may also aid in these states."

The discovery of a universal lower bound on TEE, which is always non-negative, underscores the robustness of this entanglement measure even in the presence of perturbations introduced by constant-depth circuits.

There are still uncharted territories in this field. The researchers have laid the foundation for further investigations, such as exploring the generality of noise's impact on spurious TEE, specifically the role of constant-depth circuits, and delving into the behavior of TEE at finite temperatures.

These open questions promise exciting prospects for future research in the study of quantum systems.

More information: Isaac H. Kim et al, Universal Lower Bound on Topological Entanglement Entropy, Physical Review Letters (2023). DOI: 10.1103/PhysRevLett.131.166601

Journal information: Physical Review Letters

2023 Science X Network

Read more from the original source:

Scientists demonstrate the existence of a universal lower bound on topological entanglement entropy - Phys.org

Read More..