We are scientists working on quantum computers. Ask us anything!

Hi guys, (classical) computer scientist here. I have a bit more programming language oriented question if you do not mind, I hope it makes some sense.

Considering the history of computer science, two major things evolved in parallel: hardware, and theoretical models for calculus. The study of the latter would lead notably in particular to the development of various programming languages once both branches have been mature enough.

Now in the context of quantic computer science, we hear on quite a regular basis about impressive progress on the hardware side. However on the calculus side, I am still only aware of the very "physics oriented" calculus over Hibert spaces. Would you know if alternative models have been developped, potentially sketching ideas for high level programming languages over quantic architectures?

Thanks for the AMA!

There have been a number of proposals for alternative mathematical models of quantum physics or computing and also high level programming languages.

Here is a link to one of these based on the mathematics of category theory but expressed using diagrams.

https://en.m.wikipedia.org/wiki/Categorical_quantum_mechanics

Here is an article on quantum programming languages:

https://en.m.wikipedia.org/wiki/Quantum_programming

Dan

Although we don't fully understand the question, I have the feeling that you are asking whether there is a natural way to program quantum algorithms.

Right now we have a few subroutines that we use frequently in various quantum algorithms, but that's it. We don't really have a good way to understand quantum algorithms intuitively, so we don't know how to make an intuitive high level quantum programming language. Otherwise we are mostly concerned about how to compile known high-level quantum algorithms into a sequence of gates that we can apply to concrete (quantum) physical systems.

Xiaotong Ni

I did an AMA a month ago and gave this answer to a question. Perhaps it is also relevant for you.

James

What are some examples of ways quantum computing could be used to improve things we do during everyday life?

First of all, it is very difficult to predict what a machine can do that we have not yet built. The revolution from quantum computing will surly not be as overwhelming as the revolution we have experienced with classical computers, simply because our societies are already accustomed to the principle of computing.

As of now, it seems likely that a quantum computer will be most useful as a research tool. You can compare it to the impact of a scanning tunneling microscope, which very few individuals have in their homes but has been invaluable to biology and chemistry research, which in turn has led to tremendous progress in medicine and materials.

That being said, we do expect quantum information technologies to revolutionize the field of cryptography, the manipulation of complex molecules and materials science in general. One particular example is the process of carbon capture, which is an intractable problem in physical chemistry, but might be tractable with the help of quantum computing. This could be critical in curbing the effect of global warming.

Finally, today's most powerful supercomputers have roughly the same number of transistors as the human brain has neurons. However, they consume a quadrillion (1'000'000'000'000'000) times more energy then the human brain. The technology involved in developing quantum technologies could help us bridge this energy gap, and make computing ultra cheap in terms of energy.

Michael

A very nice analogy I once read in a paper, is that quantum computers are going to be a similar revolution to classical computers, as laser light was to lightbulbs. It didn't replace them, but it opened the possibility to a huge number of applications that hadn't even been imagined before.

Mercedes

What advice do you have for a young person wanting to go into science (physics, specifically)?

A lot of research has shown that your peer group (people around you, e.g. in your classroom) is one of the biggest factors in how well you learn. Just google "peer group effect". The optimal for any student is to be surrounded by peers who are slightly more knowledgeable, and who happy to have intelligent debate. In short, having smart friends is more important than having smart teachers.

Also, the best scientists are those who do it for the pure joy of it!

On the basis of this I'd suggest the following approach: Find smart friends also interested in science and nerd out together. Find fun in talking about science and the rest will fall into place.

That and maths. Learn maths. Doesn't matter what science you do, maths will help.

Earl

Thank you so much, Dr. Earl! I'm really, really passionate about this and I aspire to be a physicist like you. You are the people shaping and changing our understanding of the world, and I admire all scientists so very much. Thank you!

You are welcome. Never stop aspiring :)

A degree in physics is a good place to start. Beyond that, you will start to form a better idea yourself what area you want to go into.

James

Bare in mind that your choice of masters project is the most important decision in your career. It largely determines your future career path Michael

Oh God I hope this isn't true. My Masters project was a complete farce and I'd be embarrassed to show it to anyone. Even worse, it's in a field I'd still like to get into, so people are going to want to read it if I pursue that. Disaster.

Please someone tell me it's common to completely distance yourself from undergraduate/Masters work!

You can still make it. We all have crap in our back catalogue. Learning from it is probably the most important thing, good or bad.

James

Have you thought about summer internships/projects in academic departments? As an undergrad, I knew I wanted to do research but didn't know in what area so I did about four different projects before settling on quantum computing. It is a great opportunity to show your interest and skills and becomes very valuable when applying for graduate programs. You also get to learn a lot about the research area and techniques. Don't give up!

Mercedes

What did you do your undergrad in?

I think all of us did their undergrad in physics. But we've got computer scientists here at the conference too. Maybe even a mathematician!

James

Does this have the kind of computing power to operate a proper molecular level 3d printer so we can finally stop screwing around and have a Star Trek-esque replicator? "tea - earl grey - hot"...dope

Quantum physics actually shows that a replicator is impossible! It is a result called the no-cloning theorem. If you first get you head around Heisenberg's uncertainty principle, then no-cloning is easy to understand.

So Heisenberg's uncertainty principle says you can't know the position and momentum of a particle. You can learn the position or the momentum, but not both at the same time.

Assume you we able to clone or replicate on the molecular level. Measure position for one of the copies and momentum for the other copy. You've learnt both the position and momentum. But this violates Heisenberg. Therefore, the quantum replicator is an impossible technology.

Earl

So Heisenberg's uncertainty principle says you can't know the position and momentum of a particle.

Ah, ah, ahhh, but the Enterprise has Heisenberg (uncertainty) compensators.

But there is that episode where the transporter breaks down so Rikker gets cloned! Which is impossible. Unless the two Rikkers are not perfect quantum clones and only classical clones.

Earl

They are only useful in the teleporters. Teleportation isn't physically impossible, just practically impossible, and the Heisenberg compensators sort that out.

Exact replication is cloning, which is against the laws of physics, and so cannot be dealt with through Heisenberg compensation.

James

Hmm...so that's a solid "no" on the replicators? I'm not gonna lie, this might be the most bummer thing I've heard this month.

Exact replication at the molecular level is a solid "no". But that won't be required for making Picard's tea.

James

Well you couldn't replicate all the way down to the quantum level. You could build an approximate replicator that doesn't make a perfect copy and by eye you couldn't see the difference. So maybe that will cheer you up a bit. But I think it is fun to think about why replication is impossible in the quantum realm.

Earl

Does this have the kind of computing power to operate a proper molecular level 3d printer so we can finally stop screwing around and have a Star Trek-esque replicator? "tea - earl grey - hot"...dope

I don't think we are the ones that will invent the replicator. But maybe some of the quantum computer's power at problems like protein folding will be of help. Until then, we'll have to make do with tea bags.

James

Would the security really improve or a quantum computer would ne able to force another 'quantic password' the same way a computer can 'bruteforce' a password today ?

Could new protocols/technologies regarding cyber security be created, making internet navigation completely safe for instance ?

The idea of quantum key distribution (QKD) is one way in which quantum systems provide enhanced security over standard (classical) systems. QKD has certain models of security where it is provably secure, but this is only a model. In the real world, the weakness in a cryptosystem is not whether the encryption is classical or quantum, but rather how it is implemented. So while quantum devices do offer some prospects for enhanced security, one should take these claims of perfect security with a grain of salt.

On the flip side, a quantum computer can indeed break the widely used RSA cryptosystem, but we are still very far from being able to implement these algorithms. So your internet transactions are most likely safe for the foreseeable future. It is a current topic of research to design classical cryptosystems that can resist a quantum attack, and there are several candidates, but nothing is yet conclusive.

Steve

What about the claims that quantum computing will break the entire cyber security and encryption system currently being used worldwide?

Another topic I'm interested is about the claim that you won't be able to have a quantum desktop computer, because the computational purpose of a quantum computer differs from a desktop. Any insight and comment on that?

For the first question, RSA encryption is the usual standard that people are referring to when they say that quantum computers will break "all" of cyber security. It's a very commonly used cryptosystem, and a fully functional quantum computer would indeed break it, but we're very far from that.

I do suspect that no one in the foreseeable future will have a quantum desktop. This is partly because we're still far from building devices with that kind of power, but also because quantum computers seem to outperform classical computers for only a relatively small set of tasks. It is likely that these tasks will be done by centralized quantum devices. Think about how a supercomputer of yore might be located in some basement of a university and people would have to apply for time on it. This will probably be the use case for quantum computers on the timescale of 20-40 years.

Steve

Another topic I'm interested is about the claim that you won't be able to have a quantum desktop computer, because the computational purpose of a quantum computer differs from a desktop. Any insight and comment on that?

The kind of applications that we currently know about are solving science questions. No-one's yet come up with something that people at home will directly need a quantum computer for.

It may be that someone will find such an application, and so there will be a drive to get you a quantum computer at home. But it probably won't be us that find it. It'll be the quantum software engineers of the future.

James

To answer your second question, it is unlikely we'd need a quantum computer on our desktops (just as we increasingly no longer need desktop computers on our desktops!) because we can easily access them remotely via the internet.

This is useful for quantum computing, since many of the leading technologies under development need to operate at temperatures close to absolute zero, so the quantum computer would need to sit inside a very very cold cryogenic fridge.

In fact, you can already access a prototype small quantum computer in this way via IBM's Quantum Experience:

http://www.almaden.ibm.com/cgi-bin/research_redirect.pl?quantum/

Dan

As Steve said, quantum-computer resistant cryptography (sometimes called post-quantum cryptography) is an active research area and Google have already included one of these candidate protocols in their latest experimental builds of Chrome. https://security.googleblog.com/2016/07/experimenting-with-post-quantum.html

Dan

Just to complement Steve's answer, even though quantum cryptography is claimed to be completely safe, there are always possibilities to circumvent the condition used in those proofs. For example, there are people studying quantum hacking

http://www.vad1.com/lab/

Xiaotong Ni

How many hours each of you usually sleep?

I get eight hours, it's tough to do research when you're groggy.

Ben

I try for 8. My kids determine the duration more than work.

James

Seven if I'm lucky - Earl

As many as I can get, but about 7.30 on average. There's only a limited number of days your brain is any use with less that 7.

Mercedes

What is the most promising technological base used to build a quantum computer / set up qubits at the moment? And do you see any other technologies coming up in the future that could be used as well?

I think we are hesitating to answer this because we don't want to break out into a fight. But the correct¹ answer is spin qubits.

James

¹ Not neccesarily correct.

Scientists around the globe are currently pursuing different technologies, and we don't have a clear winner yet, it might even be the case that a hybrid of various technologies will be the best solution! Current favourites with the community are superconducting qubits and ion traps, however, there are other physical implementations that show great promise, such as integrated linear optics, quantum dots or topological quantum computing. A deciding factor will be the ability to scale up the technology, as at the moment any of these implementations can only handle few qubits. Technologies that can benefit from microfabrication techniques (such as the ones used in computer chips today) will be at a great advantage.

If interested I recently wrote a blog post summarising the main points about the four technologies most benefited by microfabrication: https://quantaforbreakfast.wordpress.com/2016/08/03/promising-implementations-of-quantum-computers/

Mercedes

Honestly, I don't know that we've yet found the right physical hardware for large-scale quantum computers. In my opinion, the most promising candidates currently include superconductors and trapped ions. There are several other candidates: photons, semiconductor quantum dots, topological particles called anyons, and more. Currently, these other methods have some catching up to do, but really we're asking who is gonna win the marathon after the first kilometer of the race. The most likely future device will involve hybrids that incorporate the strengths of each of these while suppressing their weaknesses.

Steve

What are some of the differences between the quantum computers you research and something like Google's D.Wave?

The D-wave quantum computers are analog computational devices. The vast majority of work on these devices does not use any error correction to stabilize the system against imperfections. By contrast, the quantum computers that the rest of us are working on incorporate both error correction (fixing errors) and fault tolerance (keeping errors from spreading). These devices will be able to achieve arbitrary precision computations and are essentially digital devices, not analog.

It is a bit like the difference between simulating an aircraft wing using a wind tunnel on a scale model (that's D-wave) versus a finite element analysis digital simulation (that's a standard quantum computer).

Steve

Well, think of it as the Spaniards and Portuguese vying for discovering a direct sea route to the Indias in the 15th century. The Portuguese decided to circumvent Africa. Their first few attempts failed, but as they improved their ships and maritime technology, they eventually succeeded in circumventing Africa, and reaching India and China. They adopted a sound route, whose success relied on stepwise progress.

The Spaniards took the ships they had and sent them out in the unknown sea based on the (at that time unfounded) belief that there was no continent separating Europe and Asia from the east (contrary to popular belief, most savants of the day knew that the earth was round). They gambled with the technology they had at the time, and tried to see how far they would get with it.

We are taking the portuguese route, basing ourselves on stepwise progress to ensure that we will reach the ultimate goal of building a quantum computer.

D.Wave are adopting the spanish approach, except that they are using rafts rather than boats.

--Michael

Google does own a D-wave machine, but they are made by another company (D-wave). However, Google are also developing there own superconducting quantum computer of the universal fault-tolerant type.

Earl

Hi guys ! What if quantum computers never works ? Does your research have others application ? Could it be used in other branch of science ? Is it already useful somewhere else ?

Ideas from quantum computing have already had a large impact on related fields.

Theoretical ideas have lead to insights into computer science, mathematics, and other branches of physics. For example, "quantum proofs" of classical theorems can sometimes be simpler in a similar way that using complex analysis can sometimes give a simpler proof of a theorem in real analysis. Ideas from quantum information have lead to methods to explore the physics of condensed matter systems in new and more efficient ways.

Experimental advances are leading to technologies that, while falling short of being quantum computers, nonetheless harness quantum phenomena in useful ways. For example, quantum devices are being developed that can sense small shifts in frequency or gravitational fields, and quantum cryptography is already a commercial product.

The fact that there are many exciting intermediate milestones along the way to a full-blown quantum computer is one of the reasons why I expect that quantum computing will be a burgeoning field for decades even though we won't all have quantum computers on our desktops.

Steve

We and our research will just integrate into the closest area of physics, maths or computer science. Some research on quantum computation already has been used on unrelated problems.

James

Many of the technologies we are trying to use for quantum computing are currently used for classical purposes. Any research we do in these areas goes towards understanding these systems better and hence making them more useful. For example, research in linear optics can improve optical communications while solid state research can improve classical memories. Also, the field of quantum technology is far larger than just quantum computing, and research in quantum information will also be useful there.

Mercedes

Hey guys, I am currently going into the later years of secondary school and during this time I have finally decided to have a future career in physics, especially quantum mechanics. So during the last few months in my spare time, I've begun purchasing books explaining elements of QM and using web resources such as KhanAcademy to also further increase my knowledge. However, I don't feel like I've learnt enough from just ideas and explanations alone so I am very interested in exploring the mathematics behind QM. So my question is are there any resources you can link me which can explain some basic maths about QM or a way about learning the maths?

Thanks in advance :)

The most important areas of maths for quantum computing theory are:

*complex numbers

*matrices

*group theory

Since you use the term "secondary school" are you in the UK? I'm British too and I studied all three of these topics in secondary school as part of my Further Maths A-level. So if you are UK-based a Further Maths textbook could be a good starting point.

Dan

Edit: For example, this book covers most of that material at A-level level: https://www.amazon.co.uk/Further-Pure-Mathematics-Brian-Gaulter/dp/0199147353

"Quantum Computation and Quantum Information" by Nielsen and Chuang, "An Introduction to Quantum Computing" by Kaye, Laflamme and Mosca, "Quantum Computing since Democritus" by Aaronson, are some good books.

Christophe

How can one as an individual access quantum computing, both in terms of physically acquiring hardware and also actually being able to use it for something (anything?), and how does accessibility look to be changing in the future?

It's still a long time before individual can buy quantum computers of their own. So in the near future, individuals will likely access quantum computing in some cloud architectures. For example, IBM already has a website that allows users to access a very small quantum computer.

Also see https://www.reddit.com/r/IAmA/comments/49jkhn/im_bill_gates_cochair_of_the_bill_melinda_gates/d0sam8v

Xiaotong Ni

Would spilling water on a quantum computer break it?

It depends on the quantum computer, but a lot of the hardware that quantum computers are based on has to be sealed off from the outside world anyway. If you spilled water on the outside, likely nothing would happen. Some quantum computing experiments are even done inside these (chemist for scale), which you could splash some water on, no problem.

Ben

So twenty years ago we couldn't even dream of 10 core CPUs being accessible(-ish) to the average consumer. How long do you think it will be until we, as average consumers, will get PCs the likes of Quantum Computers into our homes?

It will likely never happen, for two reasons:

1) the tasks that quantum computers significantly outperform classical computers seems not to be useful to household or entertainment tasks.

2) By that time, most of the actually computing will not be done on your smartphone or laptop, but rather on a computing cloud.

Michael

Is there any merit to the idea of a quantum computing device helping with video game physics simulations? I've often wondered about this.

I'm not sure exactly how quantum computers might have gaming applications. Maybe it's the big secret behind the NX, and why Breath of the Wild is so delayed ;)

Thinking of gaming applications is certainly interesting, but I don't see that it will be taken too seriously. Though Microsoft has it's fingers in both pies, so we might wangle a bit of funding.

James

In another question you said it will be 50 years before there's widespread implementation of personal quantum computing. What is the biggest barrier in getting this in widespread use, and what is the status of the hardware today?

In "regular" computers, there's a hard disk which uses the stability of its small magnetic regions to store information for a long time, without consuming any energy, at room temperature. There are also logic circuits that can correct small deviations in the voltages they use to represent zeros and ones. These things mean that we can assume that the computer works while we're making up algorithms.

In a quantum computer, there are no guarantees. If you want to store a quantum bit reliably, you have to use a large number of the noisy quantum bits that exist in the lab. It's not clear what the best way is to go encode this information, or what constraints such encoding would put on the allowed processing operations. Though the hardware is getting better, and we're getting better at designing high-performance codes, it's tough to tell when these two efforts are going to start meeting in the middle.

Ben

Thx

No problem.

Ben

50 years is fairly pessimistic, though it is comparable to the time it took between the invention of the transistor and widespread desktop computing.

One big difficulty in building a quantum computer is that we must control quantum bits (qubit) stored in individual atom, electrons or photons. This control must be exquisite. But such control is really difficult. Even if you can control a single qubit with precision 99% this means that every 100 computational steps, an error will occur. In a quantum computation with millions of computational steps, the output would be garbage.

At our workshop we are working to solve this problem using quantum error correction techniques. These are methods that allow us to reduce the physical noise by storing the data in quantum code. However, quantum error correction only works if the precision is already above some level we call the threshold. Newish theory ideas give a threshold of about 99%.

The really remarkable progress in hardware has been that we are now past the 99% mark. Recent experiments in Oxford even claim 99.9% precision. So one of the biggest barriers has been overcome!

However, we have only achieved this level of precision in systems of 2-8 qubits. The barrier we face now if how to "scale up" to many millions of qubits while maintaining the small level of precision. In different hardware platforms there are different obstacles to scaling up. Hope that helps :)

Earl

Perhaps a random question, but: Have you guys ever thought about designing the hardware of a quantum computer (maybe an adiabatic one) that uses Bayesian network "logic" rather than aiming for the traditional circuit model? Would such a computer be easier to build than a gate-based one?

And one other question...AdS/CFT relies heavily on quantum information. It provides ways to describe certain field theoretic problems, on a fairly abstract level, using spacetime equations. Has this ever, have you guys ever, considered using it to, for instance, design a topological quantum computer? (and if so, are there any direct tie-ins to figuring out ideal ways for built-in error correction using this correspondence?)

I have a truly marvelous proposal for using AdS/CFT to build a topological quantum computer, but unfortunately this (3+1)-dimensional spacetime is too narrow to contain it.

Steve

Are there any applications of many-body localization to quantum computing?

Some have looked into it. Like me and others.

There'll be more recent work than that, but not that I think of atm.

James

Hello! Doing a science-project contest, and my project is on developing a programming language for classical and quantum computing.... Anything you would like to see in a language - as such?

I will shamelessly plug my stuff my suggesting you instead develop a decoding algorithm for quantum computation using /r/decodoku.

But in answer to your actual question, probably best to check out existing approaches to quantum programming languages. There's no specific wishlist I have for future ones.

James

The number of algorithms that we currently know to be exponentially more efficient on a quantum computer is limited. At the moment we are in more dearly need of good control software for the experiments, and for that, you'd require a detailed description of the experiment in question. However, computer software aimed at the control and usage of quantum computers is starting to emerge. You might be interested in Microsoft's LiQUi|> simulator and the software developed by 1QBit.

Mercedes

Classical computer programmer here, I've got a couple questions.

With all the ways we can solve problems efficiently with classical computers, and the small subset of problems that can be solved with QC, how do you guys see the synergistic relationship of CC and QC moving forward? The way I see it a QC would make a good "sub-processor" for a CC, kind of like a class in OOP, where you can call upon the QC classically to return something that would take a CC longer to compute.

What do you guys think of new computing architectures like SyNAPSE? Could tech like this combined with QC possibly alleviate concerns about the Moore's Law ceiling?

I'm working in the IT field as a Data Analyst, but I've always been endlessly fascinated with academic research. I want to contribute, but I don't want to stop working either. I'm slowly working on my BS degree after obtaining my AA recently. Is there any way I can get involved with research if I'm not a full time student?

About your last question, I do think machine learning can help the process of building quantum computers. In fact, I have a paper on using recurrent networks to help optimize some gate sequences for quantum memory.

Maybe one day we can have a Kaggle competition for quantum memory. But otherwise I would suggest you to be cautious of doing quantum computing research, as it will take a while for you to understand what are the problems we want to solve and what has been done.

Xiaotong Ni

For the foreseeable future, we'll definitely be using classical computers to control and monitor quantum ones, so you can think of quantum computers as being co-processors.

On keeping Moore's Law going, there's some consensus that you have to get beyond transistor-based logic (quantum tunnelling implies that any sufficiently small transistor would basically be a conductor), since packing the elements into three dimensions raises heat dissipation issues. One promising way forward is to store information (classical or quantum) in the spins of electrons, which are too small to measure, and even too small for any physical theory to predict their size, so there's no fundamental limit to miniaturisation (heat dissipation is still necessary, though). We don't actually know a lot about neuromorphic computing, but if it uses transistors, it's still limited by the factors I mention above.

If you want to get into quantum computing, but don't have a lot of time, you can always try decodoku. If you get the high score, you may know something we don't about quantum error correction.

Ben

If quantum computers are the future, what is the future of programming? (Worried junior programmer asking)

There is very probably a lot of programming to do in any future coming. You have nothing to worry about :).

Christophe

Is it zero or one? tell me without YOU altering the outcome.

I'll just entangle you to it. Then I didn't do anything that's not reversible, but you will know. Or both of you in different universes will know. Or something. It would be a great experiment!

James

Hi, thank you for such interesting topic! I have a lot of questions :) Where should start a classic computer scientist to master quantum computing? And what are most challenging problems today for QC to solve ?

I would recommend the book by Nielsen and Chuang as a classical computer scientists entrance to the field. But if you are interested in the complexity side, there are probably better things to read that I don't know about.

James

What is the best way to get into coding? I read a lot about apps to teach it and code dojo, would you recommend any in particular?

I do a lot of coding, but I'm no good at it. So maybe I'm not the best to answer. But I'll answer anyway.

I think the best way to start is to try programming something. Making a simple game with Unity, for example, can be done without too much trouble if you already know some basics.

James

0) Pick a language, say C.

1) Read the first few chapters of a decent text, say "Let us C".

2) Pick a fun and easy programming project and jump in even if you don't feel 100% prepared. For instance you could write your own version of the Game of Life (https://en.wikipedia.org/wiki/Conway%27s_Game_of_Life).

3) Debug until it works.

--- Earl

Second that, the only really good way is to pick something fun and attempt to code it. But I would not necessarily recommend using a book, there are loads of free online courses and resources such as codecademy.com and https://beta.hacksaw.academy that would make the process a lot less frustrating.

Mercedes

Explain quantum computing in ELI5?

Thanks

I'm not sure I can explain quantum computing to a five-year old, but here is a great book (written by a quantum computing researcher at the University of Sydney) on quantum physics for babies!

https://www.amazon.co.uk/Quantum-Physics-Babies-Chris-Ferrie/dp/1492309532

Dan

One inspiration of quantum computing is the many-world interpretation of quantum mechanics. So in some sense, you can think a quantum computer is equivalent to an exponentially many classical computers running in parallel, thus achieve a speedup. However, this explanation is not completely correct since it is very hard to extract relevant information from "the exponentially many classical computers".

Also note that nowadays many new quantum algorithms deviate from this intuition.

Xiaotong Ni

Some deep scientific stuff here, which I love to read:
"There are no particles, there are only fields" Or:
"There are no particles, there are no fields"
And it raises some questions:
Isn't the concept of particles completely false? Does light or matter actually move in particles? How is light different from a wave? What are the alternatives? Does it affect quantum computing?

Isn't the concept of particles completely false?

It depends what you mean by particles. I suppose a victorian understanding of them is false. But our current understanding is yet to be falsified.

Does light or matter actually move in particles?

Using the story (and maths) of light and matter moving in particles is helpful for predicting outcomes measurements in experiments, and also real life phenomena. So I think 'yes' is a more accurate answer than 'no' here.

How is light different from a wave?

Light is a type of wave. It's a wave in the electromagnetic field. But the energy of that wave is absorbed only in discreet chunks. So it also behaves like a particle. This is also true of other waves, like sound which can be explained in terms of particles called phonons.

For our everyday life, the size of the chunks is extremely small in comparison to the energy of light and sound that we deal with. So we don't notice the chunkiness. But all waves are chunky. And all chunks are wavy.

Does it affect quantum computing?

At some level, wave particle duality is quantum. So it makes QC possible.

James

Back in 1998 I made a bet with someone that quantum computing would be in widespread use within 10 years. I lost that bet badly. Given the state of quantum computing now, if I were to make a similar bet now, when should I bet on widespread use of quantum computers? 5 years from now? 20 years from now? 50 years from now? maybe never? Would a quantum computation algorithm help in selecting the correct timeframe? :)

It depends on what you mean by "widespread use". If you want to have a qLaptop that you can carry to the coffee shop, then you'll be waiting at least 50 years... at least 50 years. On the other hand, I suspect that in 50 years you will be able to access quantum processors remotely via the cloud. On the timescale of 5 years, we will only have very rudimentary quantum devices in my opinion perhaps with one or two logical qubits (i.e., stable encoded quantum bits). But I think that there will be many researchers that will be building and using these devices, so although the actual computational power of these devices is very small, this might qualify as "widespread".

Steve

what is the meaning of life?

I asked my quantum computer to factorize 42, and it told me 6*9. I guess my quantum error correction needs improvement.

James

Are there parts of the deep web that only quantum computer can access?

Based on the Wikipedia's description

The deep web includes many very common uses such as web mail, online banking but also paid for services with a paywall such as video on demand, and many more.

I don't think quantum computing will change search engine in a way that it can index these part of the Internet.

One should keep in mind that quantum computers are only going to excel for a small range of applications. This is not because quantum computers are not powerful, but rather classical computers already filled most roles.

Xiaotong Ni

Does quantum computing represent the best chance at P=NP? (my wording's not great but I hope you see what um getting at in terms of better/faster algorithms?)

YES ! In the sense that it is not a chance at all, like any other approach :).

Christophe

It's the best chance at beating the limitations of P!=NP on normal computers.

James

Hypothetically, if Quantum Computing was successfully achieved, would it render the P=NP problem true?

No, even if we had a full-scale working quantum computer this would still not resolve the P vs. NP problem. It's a mathematical question and no amount of physical hardware will be able to answer it conclusively.

Steve