It may be possible to control a quantum computer over the internet without revealing what you are calculating, thanks to the many possible ways that information can flow through a computation. That’s the conclusion of researchers in Singapore and Australia who studied the measurement-based model of quantum computing, reported 11 July in the open-access journal Physical Review X. Credit: Timothy Yeo / Centre for Quantum Technologies, National University of Singapore

Here’s the scenario: you have sensitive data and a problem that only a quantum computer can solve. You have no quantum devices yourself. You could buy time on a quantum computer, but you don’t want to give away your secrets. What can you do?

Writing in Physical Review X on 11 July, researchers in Singapore and Australia propose a way you could use a quantum computer securely, even over the internet. The technique could hide both your data and program from the computer itself. Their work counters earlier hints that such a feat is impossible.

The scenario is not far-fetched. Quantum computers promise new routes to solving problems in cryptography, modelling and machine learning, exciting government and industry. Such problems may involve confidential data or be commercially sensitive.

Technology giants are already investing in building such computersand making them available to users. For example, IBM announced on 17 May this year that it is making a quantum computer with 16 quantum bits accessible to the public for free on the cloud, as well as a 17-qubit prototype commercial processor.

Seventeen qubits are not enough to outperform the world’s current supercomputers, but as quantum computers gain qubits, they are expected to exceed the capabilities of any machine we have today. That should drive demand for access.

“We’re looking at what’s possible if you’re someone just interacting with a quantum computer across the internet from your laptop. We find that it’s possible to hide some interesting computations,” says Joseph Fitzsimons, a Principal Investigator at the Centre for Quantum Technologies (CQT) at the National University of Singapore and Associate Professor at Singapore University of Technology and Design (SUTD), who led the work.

Quantum computers work by processing bits of information stored in quantum states. Unlike the binary bits found in our regular (i.e., classical) computers, each a 0 or 1, qubits can be in superpositions of 0 and 1. The qubits can also be entangled, which is believed to be crucial to a quantum computer’s power.

The scheme designed by Fitzsimons and his colleagues brings secrecy to a form of quantum computing driven by measurements.

In this scheme, the quantum computer is prepared by putting all its qubits into a special type of entangled state. Then the computation is carried out by measuring the qubits one by one. The user provides step-wise instructions for each measurement: the steps encode both the input data and the program.

Researchers have shown previously that users who can make or measure qubits to convey instructions to the quantum computer could disguise their computation. The new paper extends that power to users who can only send classical bits – i.e. most of us, for now.

This is surprising because some computer science theorems imply that encrypted quantum computation is impossible when only classical communication is available.

The hope for security comes from the quantum computer not knowing which steps of the measurement sequence do what. The quantum computer can’t tell which qubits were used for inputs, which for operations and which for outputs.

“It’s extremely exciting. You can use this unique feature of the measurement-based model of quantum computingthe way information flows through the stateas a crypto tool to hide information from the server,” says team member Tommaso Demarie of CQT and SUTD.

Although the owner of the quantum computer could try to reverse engineer the sequence of measurements performed, ambiguity about the role of each step leads to many possible interpretations of what calculation was done. The true calculation is hidden among the many, like a needle in a haystack.

The set of interpretations grows rapidly with the number of qubits. “The set of all possible computations is exponentially large – that’s one of the things we prove in the paperand therefore the chance of guessing the real computation is exponentially small,” says Fitzsimons. One question remains: could meaningful computations be so rare among all the possible ones that the guessing gets easier? That’s what the researchers need to check next.

Nicolas Menicucci at the Centre for Quantum Computation and Communication Technology at RMIT University in Melbourne, Australia, and Atul Mantri at SUTD, are coauthors on the work.

“Quantum computers became famous in the ’90s with the discovery that they could break some classical cryptography schemesbut maybe quantum computing will instead be known for making the future of cloud computing secure,” says Mantri.

Explore further: Refrigerator for quantum computers discovered

More information: Atul Mantri et al, Flow Ambiguity: A Path Towards Classically Driven Blind Quantum Computation, Physical Review X (2017). DOI: 10.1103/PhysRevX.7.031004

Read the rest here:

Why you might trust a quantum computer with secretseven over … – Phys.Org

- Intel Takes First Steps To Universal Quantum Computing - October 13th, 2017
- Qudits: The Real Future of Quantum Computing? - IEEE Spectrum - October 13th, 2017
- quantum computing - engadget.com - October 13th, 2017
- Quantum Computing | Intel Newsroom - October 13th, 2017
- What will you actually use quantum computing for? | ZDNet - October 11th, 2017
- Here's what quantum computing is and why it matters - October 6th, 2017
- Microsoft just upped its multi-million bet on quantum computing - ZDNet - September 7th, 2017
- Microsoft's Aussie quantum computing lab set to scale up next-gen ... - ARNnet - September 7th, 2017
- An Entirely New Type of Quantum Computing Has Just Been Invented - Futurism - September 7th, 2017
- Quantum computing event explores the implications for business - Cambridge Network - August 30th, 2017
- Quantum Computing Is Coming at Us Fast, So Here's Everything You Need to Know - ScienceAlert - August 27th, 2017
- How quantum mechanics can change computing - San Francisco ... - San Francisco Chronicle - August 25th, 2017
- Commonwealth Bank investing in Australia's first quantum computer company - Which-50 (blog) - August 25th, 2017
- How quantum mechanics can change computing - The Conversation US - August 23rd, 2017
- Introducing Australia's first quantum computing hardware company - Computerworld Australia - August 23rd, 2017
- IEEE Approves Standards Project for Quantum Computing ... - insideHPC - August 23rd, 2017
- $495.3 Million Quantum Computing Market 2017 by Revenue Source, Application, Industry, and Geography - Global ... - PR Newswire (press release) - August 18th, 2017
- Physicists Have Made Exotic Quantum States From Light - Futurism - August 16th, 2017
- Machine learning tackles quantum error correction - Phys.Org - August 15th, 2017
- Quantum Internet Is 13 Years Away. Wait, What's Quantum Internet? - WIRED - August 15th, 2017
- Blind quantum computing for everyone - Phys.org - Phys.Org - August 12th, 2017
- Quantum Computing Is Real, and D-Wave Just Open ... - WIRED - August 12th, 2017
- Quantum Computing Market Worth 495.3 Million USD by 2023 | 08 ... - Markets Insider - August 10th, 2017
- China uses a quantum satellite to transmit potentially unhackable data - CNBC - August 10th, 2017
- Physicists Take Big Step Towards Quantum Computing and ... - Universe Today - August 1st, 2017
- Quantum-computer node uses two different ion species - physicsworld.com - July 10th, 2017
- Quantum Computers vs Bitcoin How Worried Should We Be? - The Merkle - July 10th, 2017
- Quantum cheques could be a forgery-free way to move money - New Scientist - July 10th, 2017
- Technique for measuring and controlling electron state is a ... - UCLA Newsroom - July 9th, 2017
- Quantum Computers Made Even More Powerful with New microchip generating 'Qudits' - TrendinTech - July 8th, 2017
- Quantum Computing Record Broken - Wall Street Pit - July 8th, 2017
- Alkermes and IBM's quantum computing. Who'll be the big winner? Malcolm Berko - Durham Herald Sun - July 6th, 2017
- Qudits: The Real Future of Quantum Computing? - IEEE Spectrum - IEEE Spectrum - July 1st, 2017
- Google to Achieve "Supremacy" in Quantum Computing by the End of 2017 - Big Think - July 1st, 2017
- Quantum Computing Becomes More Accessible - Scientific American - July 1st, 2017
- Tektronix AWG Pulls Test into Era of Quantum Computing - Electronic Design - June 2nd, 2017
- Toward mass-producible quantum computers | MIT News - MIT News - June 2nd, 2017
- Purdue, Microsoft Partner On Quantum Computing Research | WBAA - WBAA - June 2nd, 2017
- IBM boosts power of quantum computing processors as it lays ... - www.computing.co.uk - May 22nd, 2017
- IBM makes leap in quantum computing power - ITworld - May 22nd, 2017
- The Bizarre Quantum Test That Could Keep Your Data Secure - WIRED - May 18th, 2017
- Molecular magnets closer to application in quantum computing - Next Big Future - May 15th, 2017
- Inside Microsoft's 'soup to nuts' quantum computing ramp-up - Computerworld Australia - April 29th, 2017
- Quantum computing is about to disrupt the government contracts market - Bloomberg Government (blog) - April 22nd, 2017
- Scientists: We Have Detected the Existence of a Fundamentally New State of Matter - Futurism - April 22nd, 2017
- What Sorts Of Problems Are Quantum Computers Good For? - Forbes - April 22nd, 2017
- quantum computing - WIRED UK - April 22nd, 2017
- What is Quantum Computing? Webopedia Definition - March 18th, 2017
- Here Is Everything You Need to Know About Quantum Computers - Interesting Engineering - March 18th, 2017
- Quantum Computing Market Forecast 2017-2022 | Market ... - March 18th, 2017
- Mathematician breaks down how to defend against quantum ... - Phys.Org - February 28th, 2017

## Recent Comments