Dan Browne
Dan Browne is a Professor of Physics at University College London. His research specialism is the theory of quantum computers.
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Dan Browne replied to Gemma Church
Hi Gemma. This is a very good question. Quantum computers will have the most impact on society once they are able to be used to perform calculations impossible on today's (classical) supercomputers. When this will happen is hard to predict, but I talk about a possible timeline in Video 2.16 next week.
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Dan Browne replied to Karthick Krishnamoorthy
Welcome to the course Karthick! I hope you find it helpful. There are many post-graduate opportunities in quantum computing at the moment and I hope the course helps you get a clearer vision of the field and the state of the art.
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Dan Browne replied to Alejandra Mones Colom
Welcome to the course Ale!
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Dan Browne replied to Martin Gee
Thanks Martin! You might not be able to upload the picture, but you could post a link. It is fun to see how artists have interpreted quantum phenomena.
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Thanks for this Patrycja. I've not watched this new Black Mirror series yet. I'm curious to see how the quantum computer is presented there!
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Dan Browne replied to Angus McIsaac
To your third question, the leading algorithm for factoring large numbers on a classical computer is called the general number field sieve, whereas the leading quantum algorithm is called Shor's algorithm. The two algorithms work in completely different ways, relying on different mathematical aspects of the factoring problem.
You can find articles on both...
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Dan Browne replied to Angus McIsaac
To your second question, the answer is "yes and no". On the one hand, a perfect quantum computer can be perfectly simulated by a classical computer (although this will take memory and run time which grows exponentially in the number of qubits, so the computation may be too slow to be feasible), and on the other, a quantum computer can perform classical...
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Dan Browne replied to Angus McIsaac
Hi Angus. These are some good questions. To start with your first one, this depends what you mean by useful. After a qubit has been measured, its state will have changed (we sometimes say the state has "collapsed"), the superposition destroyed and the information it contained will have been read out. So you could say that this qubit is no longer playing an...
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Dan Browne replied to Saul Taylor
Yes it is striking how many "traditional" companies in engineering and finance are starting to take quantum computing seriously.
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This is a good summary Saul. The potential power of quantum computers is something which sometimes gets overhyped and exaggerated, and in particular you sometimes read that quantum computers might speed up all current computations, which we do not believe to be true, but you have avoided this with your careful wording. One very pedantic comment - on your last...
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Dan Browne replied to Saul Taylor
Quantum gravity is perhaps the least understood area of physics. It is very much a work in progress. Interstellar incorporated a lot of known physics (such as time dilation in gravitational fields) in the plot to an impressive degree.
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It is indeed possible to access real quantum computers at IBM over the internet. Anyone can register to do it, and I will lead a live workshop (which I recommend you sign up to) in September where we will lead participants through doing their own experiments on IBM's devices.
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The principle of superposition (sometimes described as allowing simultaneous states of 0 and 1) is absolutely key in the difference between quantum and classical computing and something which will be an important focus of the course. Quantum computers do indeed hold the potential for cracking public key encryption, due to Shor's algorithm for factoring...
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Dan Browne replied to Saul Taylor
Hi Saul. Welcome. We are glad to have you on the course. Computer science will give you a solid background for learning about quantum computing. I'm aware that many computer science departments are starting to offer quantum computing courses to their undergraduates (though usually in the 3rd or 4th year). Is Sheffield offering that?
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Dan Browne replied to Martin Gee
Welcome to the course Martin! With a Chemistry and Computing background you are well-placed to learn quantum computing. What are you most looking forward to in the course?
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I don't understand Shazam well enough to know if a quantum computer could speed it up, but this is a great suggestion. Classical artificial intelligence is making such rapid progress these days, that it is unclear whether AI really needs the help of a quantum computer. However, the idea of combining ideas from AI and Quantum is very exciting and is a very...
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Dan Browne replied to Sarah H
This is a great response. Microsoft are taking a very different path to most other companies, and it will be exciting to see if they can succeed in this approach.
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Dan Browne replied to Sarah H
Are you referring to this story: https://thenextweb.com/news/research-milestone-solve-quantum-computing-scalability ?
This is quite an exciting development indeed. There are some big challenges in realising large scale quantum computing with photons, and a significant one is that implementing quantum logic gates which generate entanglement between photons is... -
Dan Browne replied to Sarah H
You are right. That's the wrong way round! Thanks for spotting this. I will edit it.
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Dan Browne replied to Sarah H
Welcome to the course Sarah. Quantum computing has inspired quite a bit of art and music. You might be interested in this music which was composed (generated?) using a quantum computer https://www.soundclick.com/artist/default.cfm?bandID=1491038. Also check out Baba Brinkman's rap on quantum computing, written with the help of the quantum engineers at Google...
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Dan Browne replied to Sarah H
@SarahH Thanks for your comment and link. That is an excellent video for understanding binary. It is important to feel comfortable with how bits are used and how they represent numbers and information before moving on to qubits.
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Dan Browne replied to Anna Miligkou
Welcome to the course, Anna. Your computer science degree will help you! In many ways, quantum computing is very similar to classical computing, and an understanding of the basics of classical computing is essential to appreciating the differences (and therefore potential advantages) of quantum computing. Many researchers in quantum computing have a computer...
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All very good points.
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These are some good points. It is interesting to see a call for regulation in this video from two leaders of startup companies. It is usually assumed that startup companies want to be freewheeling and unencumbered by regulation, but the video shows that this is far from the case.
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@EdwardShelley Thanks. This is an entertaining and informative video.
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Dan Browne replied to Peter Darvas
Thanks very much for you kind words Peter. Entanglement is indeed one of the most fascinating and surprising aspects of quantum mechanics. It was first proposed in the 1930s by Schrödinger, and the rise of quantum computing in the mid-1990s spurred on a lot of theoretical research. Nowadays entanglement is well understood in many ways, but still continues to...
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This is a very good point. Indeed several people have predicted that quantum computing power might achieve a similar Moore's law scaling. These include the former CEO of D-wave 'Geordie Rose who posited "Rose's law" that there would be exponential scaling in quantum annealing processors, and the head of Google's quantum team Hartmut Neven proposed "Neven's...
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Dan Browne replied to David Cook
That's right. Both genetic algorithms and quantum annealers are optimisation algorithms, so there are indeed similarities between them. A key difference is that the quantum annealer is using quantum mechanical effects to "search" for the optimal solution, rather than trying many variants and picking the best.
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There are several ideas for using quantum mechanical effects for non-destructive imaging. It is a very promising area. In the UK research efforts are being led by the Quantum Imaging Hub https://www.quantic.ac.uk/aboutus/.
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We certainly see quantum computing having a cultural impact. A lot more quantum ideas are appearing in scientific fiction these days, and increasingly, I feel, in art.
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Thanks @LakhbirBawa Quantum computers have huge potential in these areas and it will be interesting to see how software engineers are able to take advantage of them.
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Thanks @PeterDarvas There is a subtle relationship between quantum computers and big data. On the one hand, quantum states can represent a lot of data at once, but both reading in and reading out this data can be slow and difficult. The most promising applications of quantum computers seem to be where the problem posed can be described by a relatively small...
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That's an interesting comment @AbdelrahimShaaban It is a very interesting question whether banks and funds will be able to gain a trading advantage by using quantum computers. There is huge potential here, and some far-sighted banks are already putting together in-house quantum computing teams to push this forward.
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That's a great suggestion @EdwardShelley . We do expect quantum computing to have a significant impact on encryption. To build a quantum computer large enough, and low-error enough to crack the public key encryption we currently use is still a very significant challenge, but it is believable that it could be here within a decade. Now is certainly the right...
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Thanks for your comment @RaunakMisra. Can you please clarify what you are asking? Is it about the heads and tails experiment in the live workshop?
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Many of the textbooks out there are at a graduate student level, but I've heard good things about Quantum Computing for Everyone by Chris Bernhardt. I've actually just ordered a copy of this book myself to check it out.
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Dan Browne replied to Josephine Magnani
Hi @JosephineMagnani, we have some suggestions for further resources in the next section 1.21. Another book that I have heard good things about (but haven't had chance to read myself yet) is "Quantum Computing for Everyone" by Chris Bernhardt.
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Thanks @LakhbirBawa, that is a good overview of the potential promise of quantum computing. We do not yet know for certain that weather modelling and financial modelling will be accelerated on quantum computing, but there is certainly a lot of interest, particularly in the latter, and major banks, such as JP Morgan and Goldman Sachs now have in-house teams...
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Dan Browne replied to David Cook
Thank you! I myself have collaborated with an artist to develop art based upon quantum technologies. In the end, an installation, based on the way data is stored using quantum cryptography, was used as a window covering on a new office building in central London! You can see it in the photos here:...
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Dan Browne replied to Ioana Macoveciuc
I hadn't thought of interpreting the skiers as being the same person. That's a very interesting perspective. There is an interesting scientific and philosophical question about whether conscious beings can be placed in a quantum superposition and what that would feel like. Currently we see know hard limit for the size of systems which can behave quantum...
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This is very good @EdwardShelley. There are subtleties in precisely what this exponential growth gives us (and it does not give us, for example, the ability to store an exponential amount of data and then retrieve it), but your summary is well caveated and a good concise summary.
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This is a good overview. It was the challenge in simulating quantum physics on conventional computers which was understood early on by Richard Feynman in the early 1980s, and his talks and articles on the topic were an important early motivation for the development of quantum computers.
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@DavidCook This is an excellent summary! You have focussed on the key points, including the important caveat that exponential speed up is only obtained in certain types of calculations.
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Thanks @PeterDarvas . The idea that quantum computers can perform many computations in parallel, and this is the source of their power is close to the truth, indeed in many key algorithms we create a superposition of multiple computational pathways. However, we can only extract the information we seek by exploiting a property called quantum interference. We do...
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Thanks @AliceJohansen. Your intuition is a good one. Exponential growth plays an important role in quantum computers' potential power, and is something we will explore this week.
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Thanks @IoanaMacoveciuc. The principle of superposition (loosely speaking being in two or more states at the same time) is at the heart of quantum computers' power and a key difference with respect to classical computers. The role of superposition and entanglement play in computation is a subtle one and still the subject of research. It is fair to say that we...
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This is a great start! I hope this course gives you a flavour of the other potential applications of quantum computers. We are still discovering what quantum computers are good at, and there are a lot of creative new ideas in this space.
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Dan Browne replied to Josephine Magnani
Welcome to the course @JosephineMagnani !
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Dan Browne replied to Alice Johansen
Welcome to the course @AliceJohansen!
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Dan Browne replied to David Cook
Welcome to the course David!
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Dan Browne replied to Ioana Macoveciuc
Hi @IoanaMacoveciuc! Welcome to the course. There are indeed many ethical issues surrounding quantum computers including who will have access to them and to what purpose? Its an interesting and important topic.
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Dan Browne replied to Peter Darvas
@PeterDarvas @DavidCook Welcome to the course to both of you. There are some similarities between quantum computing now and the earlier days of classical computers. Access to quantum computers at the moment remains quite privileged, with the notable exception of IBM who have put many of their quantum computers online for everyone to use. Which we will see in...
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Dan Browne replied to Edward Shelley
@AyanaBadrakova Welcome Ayana! How did you first hear about quantum computing?
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Dan Browne replied to Abdelrahim Shaaban
That is a beautiful image. Quantum effects have inspired some impressive art over the years. In London, there is a sculpture "Quantum Cloud" in the Thames, near to the Millennium Dome, which was inspired by Anthony Gormley's discussions with quantum physicists. https://en.wikipedia.org/wiki/Quantum_Cloud
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Dan Browne replied to Edward Shelley
This is a very nice explanation. I hadn't appreciated the importance of the "observing" skier, but he is playing a central role, as you rightly state!
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One of the inventors of quantum computing David Deutsch has written a popular book "Fabric of Reality" where he discusses quantum computing, virtual reality and potential links between them. It is a fascinating read, and was one of the books which inspired me to enter the field.
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There has been a lot of study on the philosophy of quantum physics ever since its first discovery. It raises some challenging questions about reality.
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Dan Browne replied to Edward Shelley
That is very interesting. I watched some of Devs but didn't make it through enough episodes to see if the machine they were building was a quantum computer. Certainly the machine looked a bit like a superconducting quantum computer in a dilution fridge, and must have been inspired by this. Simulation is an important potential application of quantum computers,...
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Thanks for your comments Abdelrahim. Those are some good descriptions. What do you mean by supernatural here? Quantum computing is built upon the laws of nature, although using laws (quantum physics) which are rather far from our direct human experience.
Why did you pick those particular applications?
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Dan Browne replied to Abdelrahim Shaaban
Welcome to the course Rahim!
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Dan Browne replied to Edward Shelley
Welcome Edward! I hope the course helps you build up that intuition, and you enjoy it!
