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Toward optical quantum computing – MIT News

Ordinarily, light particles photons dont interact. If two photons collide in a vacuum, they simply pass through each other.

An efficient way to make photons interact could open new prospects for both classical optics and quantum computing, an experimental technology that promises large speedups on some types of calculations.

In recent years, physicists have enabled photon-photon interactions using atoms of rare elements cooled to very low temperatures.

But in the latest issue of Physical Review Letters, MIT researchers describe a new technique for enabling photon-photon interactions at room temperature, using a silicon crystal with distinctive patterns etched into it. In physics jargon, the crystal introduces nonlinearities into the transmission of an optical signal.

All of these approaches that had atoms or atom-like particles require low temperatures and work over a narrow frequency band, says Dirk Englund, an associate professor of electrical engineering and computer science at MIT and senior author on the new paper. Its been a holy grail to come up with methods to realize single-photon-level nonlinearities at room temperature under ambient conditions.

Joining Englund on the paper are Hyeongrak Choi, a graduate student in electrical engineering and computer science, and Mikkel Heuck, who was a postdoc in Englunds lab when the work was done and is now at the Technical University of Denmark.

Photonic independence

Quantum computers harness a strange physical property called superposition, in which a quantum particle can be said to inhabit two contradictory states at the same time. The spin, or magnetic orientation, of an electron, for instance, could be both up and down at the same time; the polarization of a photon could be both vertical and horizontal.

If a string of quantum bits or qubits, the quantum analog of the bits in a classical computer is in superposition, it can, in some sense, canvass multiple solutions to the same problem simultaneously, which is why quantum computers promise speedups.

Most experimental qubits use ions trapped in oscillating magnetic fields, superconducting circuits, or like Englunds own research defects in the crystal structure of diamonds. With all these technologies, however, superpositions are difficult to maintain.

Because photons arent very susceptible to interactions with the environment, theyre great at maintaining superposition; but for the same reason, theyre difficult to control. And quantum computing depends on the ability to send control signals to the qubits.

Thats where the MIT researchers new work comes in. If a single photon enters their device, it will pass through unimpeded. But if two photons in the right quantum states try to enter the device, theyll be reflected back.

The quantum state of one of the photons can thus be thought of as controlling the quantum state of the other. And quantum information theory has established that simple quantum gates of this type are all that is necessary to build a universal quantum computer.

Unsympathetic resonance

The researchers device consists of a long, narrow, rectangular silicon crystal with regularly spaced holes etched into it. The holes are widest at the ends of the rectangle, and they narrow toward its center. Connecting the two middle holes is an even narrower channel, and at its center, on opposite sides, are two sharp concentric tips. The pattern of holes temporarily traps light in the device, and the concentric tips concentrate the electric field of the trapped light.

The researchers prototyped the device and showed that it both confined light and concentrated the lights electric field to the degree predicted by their theoretical models. But turning the device into a quantum gate would require another component, a dielectric sandwiched between the tips. (A dielectric is a material that is ordinarily electrically insulating but will become polarized all its positive and negative charges will align in the same direction when exposed to an electric field.)

When a light wave passes close to a dielectric, its electric field will slightly displace the electrons of the dielectrics atoms. When the electrons spring back, they wobble, like a childs swing when its pushed too hard. This is the nonlinearity that the researchers system exploits.

The size and spacing of the holes in the device are tailored to a specific light frequency the devices resonance frequency. But the nonlinear wobbling of the dielectrics electrons should shift that frequency.

Ordinarily, that shift is mild enough to be negligible. But because the sharp tips in the researchers device concentrate the electric fields of entering photons, they also exaggerate the shift. A single photon could still get through the device. But if two photons attempted to enter it, the shift would be so dramatic that theyd be repulsed.

Practical potential

The device can be configured so that the dramatic shift in resonance frequency occurs only if the photons attempting to enter it have particular quantum properties specific combinations of polarization or phase, for instance. The quantum state of one photon could thus determine the way in which the other photon is handled, the basic requirement for a quantum gate.

Englund emphasizes that the new research will not yield a working quantum computer in the immediate future. Too often, light entering the prototype is still either scattered or absorbed, and the quantum states of the photons can become slightly distorted. But other applications may be more feasible in the near term. For instance, a version of the device could provide a reliable source of single photons, which would greatly abet a range of research in quantum information science and communications.

This work is quite remarkable and unique because it shows strong light-matter interaction, localization of light, and relatively long-time storage of photons at such a tiny scale in a semiconductor, says Mohammad Soltani, a nanophotonics researcher in Raytheon BBN Technologies Quantum Information Processing Group. It can enable things that were questionable before, like nonlinear single-photon gates for quantum information. It works at room temperature, its solid-state, and its compatible with semiconductor manufacturing. This work is among the most promising to date for practical devices, such as quantum information devices.

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Australian push to make decryption easier ‘could threaten global … – The Guardian

Malcolm Turnbull and George Brandis, who wants to force device and social media companies to collaborate with authorities on decryption. Photograph: Mike Bowers for the Guardian

An Australian push to persuade western intelligence partners to make it easier to decrypt messaging services and devices could threaten global internet security, privacy and free speech advocates have warned.

Australias attorney general, George Brandis, said this week he would approach the Five Eyes intelligence network made up of the US, the UK, Canada, New Zealand and Australia to consider imposing greater legal obligations on device manufacturers and social media companies to cooperate with authorities in decrypting communications.

Brandis pointed favourably at UK laws that require manufacturers and messaging providers to give greater assistance to authorities in decrypting messages.

But Jim Killock, the executive director of Open Rights Group, said such an agreement could threaten global internet security and warned it might become a template for countries with poor human rights records.

We need assurances that demands for companies to modify their products do not put users security at risk, he said. There needs to be clear regulation and oversight of these notices, with companies being given the opportunity to appeal demands that are unreasonable.

The Snowden leaks showed how close arrangements between Five Eyes countries can undermine the proper oversight and regulation of surveillance capabilities at a national level.

Shahid Buttar, the director of grassroots advocacy at the Electronic Frontiers Foundation, said the efforts could not only jeopardise internet security but also the freedom of expression on which democracy rests. But the attempts would also be futile, he said.

Any country that tries to criminalise the use of math to encrypt communications will ultimately encourage people seeking privacy to migrate to competing services based in other countries.

Privacy Internationals legal officer, Scarlet Kim, said: Malcolm Turnbull has made some points about balancing the rights of innocent people against the rights of terrorists. But that balance is not an accurate picture of how decryption mandates play out.

When you undermine encryption youre undermining a core security measure that protects all of our communications. To the extent that the government thinks it can undermine encryption for a small subset of people, [that] is basically a fallacy.

Kim said Brandis should be discussing encryption with the public, not the intelligence community.

Australians need to be involved in this discussions, she said. Its quite worrisome that Australia would push this debate up to a level when even at the domestic level its not really clear what the reason is for justifying these powers.

The Australian government says the measures would help security services with terrorism investigations.

The government also has telecommunications laws before the parliamentary intelligence committee. The telecommunications industry has argued they give broad discretion to the attorney general and security services to monitor and police telecommunications infrastructure.

Guardian Australia understands Labor has not yet committed to supporting the national security proposals.

Malcolm Turnbull warned parliament this week that encryption was vital for all users of the internet but also hampered terrorism investigations.

We need even stronger cooperation from the big social media and messaging platforms in the fight against terrorism and the extremism which spawns it, he said. Encryption, for example, is a vital piece of security for every user of the internet, protecting all of us as we go about our lives, from shopping, to banking, to chatting online.

However, encrypted messaging applications are also used by criminals and terrorists. At the moment much of this traffic is difficult for our security agencies to decrypt and indeed for our Five Eyes partners as well.

Brandis declined to comment.

Contact Paul Farrell securely using the Signal messaging app on +61 457 262 172 or over email at paul.farrell@theguardian.com

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EU deals Theresa May encryption setback as MEPs propose ban on government backdoors – Telegraph.co.uk

After the attack the Home Secretary Amber Rudd accused WhatsApp of giving terrorists "a place to hide and said it was completely unacceptable that they could communicate in secret.

This week, Ms Mayand French presidentEmmanuel Macron vowed tougher action on tech companies applying encryption.

As well as outlawing encryption backdoors, the MEPs propose forcing communications providers that do not currently encrypt communications to do so.

Service providers who offer electronic communications services should ensure that such electronic communications data are protected by using specific types of software and encryption technologies,the proposals state.

A Home Office spokesman said: "The Government has been clear that we support the use of encryption. It helps keep peoples personal information safe and ensures secure online commerce.But we have also been clear that we must ensure that, in tightly proscribed circumstances, our law enforcement and security and intelligence agencies are able to access communications of criminals, including terrorists."

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Jetico’s BestCrypt Container Encryption for Linux – Linux Journal

Cyber-attacks are now constant, threats to privacy are increasing, and more rigid regulations are looming worldwide. To help IT folks relax in the face of these challenges, Jetico updated its BestCrypt Container Encryption solution to include Container Guard.

This unique feature of Jetico's Linux file encryption protects container files from unauthorized or accidental commandslike copying, modification, moving, deletion and re-encryptionresulting in bolstered security and more peace of mind. Only users with the admin password can disable Container Guard, increasing the security of sensitive files.

The BestCrypt update also adds the Resident feature, an automatic password prompt for mounting containers at startup. That same feature will dismount containers after a time period of inactivity as set by the user.

While user-friendly and time-saving, these added features also provide an extra layer of protection when working on shared computers. On endpoints or in the cloud, data encrypted with BestCrypt can be accessed via Linux, Android, Windows and Mac devices.

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Facebook defends encryption, says it is countering terrorism using AI – SC Magazine

"There's no place on Facebook for terrorism. We remove terrorists and posts that support terrorism whenever we become aware of them," reads a new Facebook company blog post.

Aware that terrorists take advantage of social media to spread propaganda, Facebook on Thursday divulged some of its methods for combating the problem, including recent efforts to employ machine learning to automatically identify objectionable content.

"Our stance is simple: There's no place on Facebook for terrorism. We remove terrorists and posts that support terrorism whenever we become aware of them," states a company blog postauthored by Facebook officialsMonika Bickert, director of global policy management, andBrian Fishman, counterterrorism policy manager.

The post came shortly after news broke that James Hodgkinson, the man who on Wednesday shot and critically injured House Majority Whip Steve Scalise at a baseball practice, regularly posted angry extremist views on Facebook regarding President Donald Trump and other Republicans. That same Wednesday, Facebook removed Hodgkinson's online profiles, according to various reports.

Facebook on Thursday also acknowledged the controversy surrounding terrorists who use encrypted messaging platforms such as the company's WhatsApp service tosecurely communicate with each other. It was following the March 2017 Westminster terror attack that British home secretary Amber Rudd suggested that UK law enforcement must be able to listen in on WhatsApp conversations, after it was discovered that the attacker, Khalid Masood, used the service before murdering four people.

Defending encryption technology, the blog post notes that these services also have legitimate purposes such as protecting the privacy of journalists and activists. In their joint blog post, Bickert and Fishman wrote that while Facebook does not have the ability to read encrypted messages, "we do provide the information we can in response to valid law enforcement requests, consistent with applicable law and our policies."

Prior to Thursday's post, Facebook had not previously detailed its use of AI to root out terrorist activity on its platforms. According to the post, the company is focusing its most cutting-edge machine-learning techniques on curbing terrorist content submitted by ISIS, Al Qaeda, and related affiliates, adding that its efforts are "already changing the ways we keep potential terrorist propaganda and accounts off Facebook."

Facebook reported that its AI technology allows its systems to image-match photos or videos that have previously been linked to terrorism, and reject such forbidden content before it is displayed.

The company is also experimenting with natural language recognition capabilities in order to identity content that appears to advocate for terrorism. To that end, Facebook has been feeding previously flagged content toits AI engine so that it does a better job recognizing such language in the future.

Additionally, Facebook is using algorithms to determine if various pages, posts, profiles and groups likely support terrorism based on connections and shared attributions with other confirmed terrorist pages. The company also claims it is getting faster at detecting new fake accounts created by repeat offenders.

Facebook has also begun to apply these AI techniques to take down terrorist accounts additional platforms, including WhatsApp and Instagram. "Given the limited data some of our apps collect as part of their service, the ability to share data across the whole family is indispensable to our efforts to keep all our platforms safe," the blog post reads.

Outside the realm of AI, Facebook is also relying on its own human expertise to counter terrorism activity online, including its global Community Operations teams that review user complaints and reports, more than 150 terrorism and safety specialists, and a global team that was formed to promptly respond to emergency law enforcement requests. The company also relies in cooperation with industry partners, governments and various community groups and non-governmental organizations.

Companies are increasingly turning to AI and automation technologies to fight a variety of illegal and forbidden online activity. A new study released this week by cybersecurity and application delivery solution provider Radware found that 81 percent of surveyed executives reported that they either recently implemented or began more heavily relying on automated solutions. Moreover, 57% of these polled executives said that they trust automated systems as much or more than humans to protect their organizations. And 38 percent predicted that automated security systems would be the primary resource for managing cyber security within two years.

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Which Altcoins To Buy This Week (16th of June, 2017) – Live Bitcoin News

The past week witnessed a massive decline in bitcoins price, which was accompanied also by a bearish wave that affected many altcoin markets. However, several altcoins surged last week to unprecedented levels. Ethereums price skyrocketed to record a new historical high of $407, before dropping down to $350 as this update is being written. Golems GNT price surged to 23,142 satoshis, before dropping slightly to 22,276 earlier today. Ethereum Classics ETC price increased to record 785,000 satoshis on Poloniex last Monday, before stabilizing around the 702,000 satoshi level, at the time of writing of this article.

So, what are the most promising coins for this week?

Bitshares surged last week to record a high of 17,675 satoshis, before the upwards trend was reversed taking price down to 9,500 satoshis. By examining the 4 hour BTSBTC chart from Poloniex and executing the Bollinger bands indicator, we can notice the following:

I recommend buying BTS between 11,661 and 12,200 satoshis and setting a sell order for the bought coins at 13,300 satoshis or even higher at 13,953 satoshis.

NXTs price surged last week to record a high of around 9,000 satoshis on Poloniex last Tuesday, before the markets bears pulled price down to 6,600 satoshis at the time of writing of this article. Lets examine the 4 hour NXTBTC chart from Poloniex, while executing the Williams Alligator indicator. We can note the following:

I recommend buying NXT between 6,500 and 6,800 satoshis and setting a sell order for the bought coins at 7,256 satoshis or even at 9,000 satoshis

Charts from Poloniex, hosted on Tradingview.com

About Dr Tamer Sameeh

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Bitcoin Millionaires And Newton’s Mistake – Forbes


Forbes
Bitcoin Millionaires And Newton's Mistake
Forbes
Congratulations Bitcoin millionaires. You made your first and perhaps your second million of dollars -- quickly, very quickly. Perhaps in the last six months in the Bitcoin investment trust. Now make sure that you don't lose all that money faster than ...

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BIP91: The SegWit Activation "Kludge" That Should Keep Bitcoin Whole – Bitcoin Magazine


Bitcoin Magazine
BIP91: The SegWit Activation "Kludge" That Should Keep Bitcoin Whole
Bitcoin Magazine
Bitcoin's long-lasting scaling debate appeared to be heading toward a climax lately, with two proposals gaining significant traction. At one end of the fence there is Bitcoin Improvement Proposal 148 (BIP148), a user activated soft fork (UASF ...
Bitcoin Scaling Proposal Segwit2x Moves Ahead With Initial Code ReleaseCoinDesk

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August 1st And The End Of Bitcoin? – Winklevoss Bitcoin Trust ETF … – Seeking Alpha

Before we get started, let me try and define some very important terms, which I hope will make it easier for me to fully convey what exactly is going to happen on August 1st.

Hard Fork - A hard fork is a permanent divergence in the blockchain, that occurs when non-upgraded nodes can't validate blocks created by upgraded nodes that follow newer block validation rules. This can be caused by a change in a blockchain's protocol that makes previously invalid blocks/transactions valid, and as such requires all nodes or users to upgrade to the latest version of the protocol software. This essentially creates a fork in the blockchain, one path which follows the new, upgraded blockchain, and one path which continues along the old path. Generally, after a short period of time, those on the old chain will realize that their version of the blockchain is outdated or irrelevant and quickly upgrade to the latest version.

Soft Fork - A soft fork is a change to the bitcoin protocol where some previously valid blocks/transactions are made invalid, and the rest of the previously valid blocks/transactions are kept valid. Old nodes will still recognize the new blocks as valid. Soft forks don't require any nodes to upgrade since all blocks with the new soft-forked rules also follow the old rules, therefore old clients accept them. This kind of fork requires only a majority of the miners to upgrade in order to enforce the new rules.

(Image Source: Bitcoin.org)

User Activated Soft Fork (UASF) - A UASF is a soft fork activated on a specified date, enforced by node enforcement instead of miner signaling. The idea is to have the economic majority, businesses and users (not miners) choose whether or not to activate this soft fork within their Bitcoin software client. On the proposed time, clients that have activated the soft fork will only accept blocks mined from miners that have also updated to start signaling for the soft fork, and will reject blocks that were created from miners that had not updated. Clients that have not updated to activate the soft fork will accept blocks mined from both miners that have updated and miners that have not updated.

By the specified date, miners are then given an opportunity to make a choice of their own, based on how much of the economic majority has activated the soft fork. If the economic majority upgrades, then miners have an economic incentive to update, as not following along would make it more difficult to sell coins mined after the chosen date, as the blocks would not be accepted by the economic majority. Essentially, miners on the old platform would be producing an altcoin not recognized by the majority of users and exchanges, making them less useful and in lower demand. Because of how the Bitcoin network only follows the longest blockchain, if a majority of hash power follows the soft fork, all nodes will follow the soft fork chain regardless of if they have updated or not, and the UASF is successful.

However, if the vast majority of the economic majority does not upgrade, then the UASF will have given miners no additional incentive to upgrade and thus miners will not update or they risk following fork rules that are or will surely be obsolete. And in fact, any of the economic majority that had upgraded now must roll back their clients to the old version, else they would be unable to spend their Bitcoin. Their updated clients would reject any blockchain that includes any non-upgraded blocks created past the specified date, so any transactions they attempt to make will be added to the soft forked blockchain which would be maintained by the soft forked nodes and miners (if there are any soft forked miners at all). This soft forked blockchain will undoubtedly remain shorter than the original blockchain containing the non-updated blocks. Thus, the soft forked blockchain will never be accepted by the non-updated clients, and the transactions of the updated clients will never be included in the original blockchain; the transactions from the updated clients will never go through.

In the unlikely case that neither side is the clear winner, this is where it gets messy. A chain split will occur, where two versions of the blockchain will emerge. All coins that existed prior to the chain split will exist on both chains. If the original "legacy" blockchain remains longer, any coins mined under the soft forked blockchain will be nonexistent according to the legacy chain, and will only exist on the soft forked chain. However, if the soft forked chain ever becomes one block longer than the original, "legacy" chain, all transactions on the legacy chain that occurred between the time of the split and the soft forked chain getting longer will be erased forever and replaced with those of the soft forked chain, at which point the soft forked blockchain will likely remain victorious.

I hope there remains no confusion over my definitions, especially so in my defining of a UASF. I will attempt to answer any questions in the comments in order to further clarify.

August 1st, and the Future of Bitcoin

Bitcoin Improvement Proposal 148 (or BIP148 for short) is a UASF that encourage users to push miners to upgrade to SegWit. SegWit, along with fixing third party transaction malleability allowing for sidechains to be developed, will also improve Bitcoin's scalability over both the short term and the long term, as the malleability fix will allow for the implementation of Lightning Network, a more permanent solution to Bitcoin's transaction speed bottleneck. As Bitcoin is a decentralized system, here's how SegWit is supposed to activate: In any consecutive chain of blocks that are 2016-blocks long, ending November 15th, 2017, 95% or more of mined blocks must signal that the miners are ready for SegWit. If that doesn't happen, SegWit activation dies. Once SegWit signaling meets the criteria, there's a 2016-block long "pause" where SegWit activation is pending, but voting no longer matters. After that point, the network will accept SegWit transactions and miners are expected to accept them into blocks.

BIP148 will activate on August 1st, 2017. All BIP148 does, is refuse to accept blocks that do not signal SegWit-ready after August 1st, 2017, either until SegWit activates or until the deadline of November 15th, 2017 hits. In so doing, it forces the existing activation mechanism to deploy SegWit. From that date on, miners that want their blocks to be accepted by nodes that have updated to BIP148 will be required to signal readiness for SegWit by switching to the creation of blocks with a new version, called 'bit 1'. After enough miners are mining 'bit 1' version blocks, enough so that 95% or more of mined blocks in any 2016-block chain are of the version 'bit 1', the above requirements for SegWit activation will be fulfilled. Then all SegWit ready nodes, which currently make up over 80% of the network, will activate and begin SegWit enforcement, and thus SegWit will have been successfully implemented into the Bitcoin Network.

(Image Source: uasf.co)

As a soft fork, BIP148 avoids having to force most users to upgrade their software. Also, the way BIP148 and SegWit are designed, once SegWit is activated, users who are not running BIP148 will still get the benefits of the activation of SegWit.

Possible Scenarios

A confrontation will happen on August 1st, but right now the exact outcome is unknown because the outcome will depend on the amount of support that miners give to the two sides. There are three possible outcomes:

BIP148 fails with very little economic majority support. BIP148 requires support from the economic majority, particularly exchanges and wallets. If this does not occur, users will not run BIP148 node software after August 1st so as to prevent a chain split. There are strong economic incentives in the Bitcoin system for nodes to cooperate and remain in consensus to prevent chain splits. If no nodes are running BIP148, then BIP148 has failed. Bitcoin goes on exactly as it did on July 31st. People who installed BIP148 nodes need to roll back their nodes to be able to spend their bitcoins. Everyone else is unaffected.

Neither side is the clear winner and the blockchain splits, where two versions of the blockchain emerge. This is the disaster scenario. All coins that existed prior to the chain split will exist on both chains. If there is a greater demand for the blocks produced by the BIP148 miners, then profit-driven miners would eventually flock to BIP148 chain and if the BIP148 chain ever becomes one block longer than the legacy chain, as in it accumulates the most proof of work, all transactions on the legacy chain that occurred between the time of the split and the BIP148 chain getting longer will be erased forever and replaced with those of the BIP148 chain. This is because both BIP148 nodes as well as legacy nodes would switch to the BIP148 blockchain, discarding the legacy chain. If 50% of the mining power goes to the BIP148, it will almost certainly become the only chain. Nobody will want to mine or transact on a chain where the mining reward and transactions can disappear at any moment forever. But unless and until this happens, there is always at least a theoretical risk that the legacy blockchain can be overtaken and be discarded like this. That chance should decrease as time goes on, but will realistically exist for hours, days, or maybe even longer. If the demand is less for the soft-fork chain, then both chains may co-exist indefinitely. BIP148 nodes will never acknowledge the legacy chain, so these nodes will not switch to the legacy blockchain regardless of which chain has more hash power. However, it is very risky to buy, accept or hold any of the BIP148 Bitcoin, too. Most importantly, there is no guarantee that BIP148 Bitcoin will continue to be used and thus the coin's long-term value is in contention.

Most likely, one of the first two scenarios will unfold, where BIP148 either succeeds triumphantly or fails definitively, and Bitcoin will go on as it were, for better or for worse. Yet despite the odds, however improbable, an investor must always consider the worst case scenario in his or her risk-reward evaluation and examine if taking on the according risk-reward is appropriate for the goals of his or her portfolio.

Disclosure: I am/we are long BTC.

I wrote this article myself, and it expresses my own opinions. I am not receiving compensation for it (other than from Seeking Alpha). I have no business relationship with any company whose stock is mentioned in this article.

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Bitcoin is suddenly on pace to have its worst week since 2015 – MarketWatch

After surging briefly to an all-time high of $3,000, bitcoin has been undergoing a dazzling reversal of late, with the digital currency on track to post its worst weekly decline in more than two years.

Bitcoin BTCUSD, +1.74% has dropped 18.5% over the past week to a value of $2,317, which would mark its steepest weekly decline since Jan. 16, 2015, according to WSJ Market Data Group. Thursdays more-than-15% drop would represent its largest one-day plunge since Jan. 14, 2015.

Put another way, bitcoin has shed more than $10 billion in market value since the start of the week, based on data from CominMarketCap, which tracks the value of digital currencies. Thats a loss just a little under Twitter Inc.s TWTR, -0.95% market cap of $12 billion.

The retreat for bitcoin, which fell to an intraday low, down about 20% at $2,076.16, also coincides with a broad selloff in the technology sector XLK, -0.17% which has finished down for four of the past five trading sessions as some of the darlings of the spaceFacebook Inc. FB, +0.56% Apple Inc. AAPL, -1.40% Amazon.com Inc. AMZN, +2.44% Netflix Inc. NFLX, +0.41% and Google-parent Alphabet Inc. GOOG, -0.27% , GOOGL, -0.16% known colloquially on Wall Street as FAANG stocks, pullback from or near record heights.

That downshift has helped to yank the Nasdaq-100 index NDX, -0.34% representing the 100 largest tech names, the Nasdaq Composite Index COMP, -0.22% the S&P 500 index SPX, +0.03% and the Dow Jones Industrial Average DJIA, +0.11% lower.

Read: MarketWatchs snapshot of the markets

Market bears have increasingly cited the up-until-now unfettered rise of both bitcoin and tech, with the heart of the digital currency, which is based on the so-called blockchain or ledger, being rooted in the very sector that has been recently getting mauled.

As an investment, separate from other fiat currencies like the dollar DXY, -0.33% or the EURUSD, +0.4666% bitcoin has benefited from its position as a decentralized currency, which also offers commodity-like elements, similar to gold GCQ7, +0.05%

But as the asset has risen, Wall Street analysts have sounded alarm bells, with Morgan Stanley as recently as this week, making the case that the cryptocurrency, which is seen as a sort of Wild West of currencies, can justifiably rise no further until its becomes more regulated.

It is not clear why cryptocurrencies are appreciating so rapidly (apart from the appreciation itself drawing in more speculation against a potentially inefficient ability to sell), Morgan Stanley warned.

Broader acceptance so far may be a while away, given the Securities and Exchange Commission in March rejecting a pair of funds that would have been underpinned by bitcoin, citing a lack of oversight and transparency.

Bitcoin and other digital currencies, including ethereum, litecoin and others, are underpinned by the so-called blockchain, which is a peer-to-peer network, or ledger, that records and verifies transactions.

Other digital currencies have been under siege as well. Ethereum, and its currency known as ether, threatening to overtake bitcoin in market value, also experiencing a sharp daily downturn, off 10.6%, according to data from digital currency site Coindesk.com. However, over the past week, ether are up 21% and has been mounting a steady ascent.

Read: How cryptocurrency ethereum looks set to overtake bitcoinin one chart

How long this slump for bitcoin, and for that matter the broader tech sector, will last is anyones guess.

However, one bitcoin watcher, Yves Lamoureux, who also predicts that one bitcoin could be worth $25,000, is near-term bearish. He predicts that bitcoin may tumble another 22% to around $1,800.

We think Bitcoin is worth more like $1,800, according to our model at this stage, and so its time to step back and stay liquid, he said.

Brian Benner contributed to this article

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