One Step Closer to Post-quantum World

One Step Closer to Post-quantum World

Urmila Mahadev, a graduate student at UC Berkeley, has come up with a solution to a major problem in quantum computation. She has found a way, using only classical computers, to know whether a quantum computer precisely follows given instructions

Intro to quantum computers

A computer is a machine that does calculations. Whether you are watching a Youtube video, writing an essay or playing a game, all your computer does is just add, subtract, multiply and divide numbers. Your computer does these calculations with the help of small electrical parts called transistors that act as switches. These switches are combined into logic gates, and logic gates in turn are connected to each other to form adding, subtracting, multiplying, and dividing mechanisms.

In our normal world, switches can be either on or off, electricity is either flowing through the circuit or not. We sometimes hear that computers work only with 0s and 1s because they store information of switches being off and on in bits that can be either 0 or 1 at one point in time. In the world of quantum physics, however, it is not that simple. A quantum object can actually be in different states at the same time or, more scientifically, the object can be is a superposition of different states. A famous example of a quantum object is Schrödinger's cat. This cat lives in a closed box. Inside that box there is also a deadly mechanism that may or may not activate. And until you, an outside observer, open that box, the cat is dead and alive at the same time. This cat is in the superposition of being dead and alive.

Quantum computers use quantum bits, or qubits. Qubits are quantum objects, usually electrons of atoms, that are spinning chaotically in each and every direction at the same time! If this is hard for you to grasp, do not worry. As some physicists say, 'It’s not that you understand it, you just get used to it'. So when qubits are spinning in all directions, we can think of them as rapidly alternating between 0 and 1. This along with a number of other curious properties such as entanglement of quantum objects are harnessed by special complex machines called quantum computers to conduct efficient calculations. Quantum computers may bring us closer to discovering the secrets of the universe by, for example, simulating black holes and protein folding, which are very computation-heavy operations.

Problem with quantum computers

The major problem with quantum computation is that we do not know how to check whether a quantum computer did all the instructed calculations or even generated the correct result. With classical computers this is really easy — all you need to do is check every step, you check every time a bit is 0 or 1. Quantum computation, however, does not have steps because it performs all steps at the same time and stops the moment you measure the result. Again, you cannot know whether the cat is dead or alive, until you open the box. Similarly, you cannot see whether the qubit is 0 or 1 without measuring it. Measurement collapses the superposition into a single unambiguous state. So, in a way, a quantum computer is a quantum computer only when you don’t look at it. As soon as you look at the qubits, they become classical bits. So if you cannot follow the process of computation, how do you know if the computation was correct?

Proposed Solution

Urmila Mahadev proposes a solution that predicates on a simple idea that if a quantum computer can do something that classical one can’t, we can still use classical means to check the result. As such we can construct such a function that is very hard to compute but is easy to verify, a trapdoor function.

For example, it is believed that quantum computers are really good at factoring numbers. For classical computers given a large number it is incredibly difficult to find its factors. This is the biggest pillar of modern cryptography. It takes a big number, a private key, multiplies it by another big number and outputs the third even bigger number, the public key. You can feed this public key to a computer but it will take hundreds of years to find its factors. But if a quantum computer does in fact find these factors, we can simply check the result by multiplying the generated numbers, which any classical computer can do. To illustrate we will use smaller numbers. We can have the quantum computer find factors of 2047 and when it gives 23 and 89, we can simply multiply those to verify the result.

Urmila Mahadev has come up with an interactive protocol that allows classical computers to verify quantum computation. They can do it by having the quantum computer measure its own qubits and output the result. For a while, the problem with this was the fact we could not trust the computer because we could not tell which superposition of superpositions the computer measured. Urmila implements the trapdoor function to first generate the output of a certain superposition and verify if qubit measurement belongs to that superposition.

Urmila approaches this problem using cryptography known as Learning with Errors cryptography which is a topic for another article. But nevertheless this is a big discovery that once again proves the sheer power of cryptography and prepares us for the post-quantum world.

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Will Quantum Computers Ever Replace The Humble PC in Our Living Rooms?

Photo by Lorenzo Herrera on UnsplashOnce only accessible to researchers at universities around the world, beginning in the late 1970s, the PC — due to a shift in size and cost — became easily available to the masses. Now that we are on the cusp of the age of quantum computers, will the same thing happen to them?Early Dawn‘The future isn’t what it used to be’, French poet Paul Valery once said, and this statement couldn’t be truer than today. We are on the rise, humanity, that is, and it’s all because of the new horizon of technology, a giant of the future, quantum computers, that is the cause. Years ago, in the embryonic days of computer development, the dream of mathematicians and scientists was humble enough: to number crunch simple computational operations. Konrad Zuse’s Z4, built in 1944, was such a machine. From that, scores of rudimentary computers followed in Z4’s wake.Konrad Zuse’s Z4 computer. Source: alamy stock photoLater, in the 1960s, two computer scientists, Thomas E. Kurtz and John G. Kemeny, based at Dartmouth College, developed and authored the BASIC language, a simple computer language which allowed ordinary people without specialist knowledge to computer program. Since those salad days, the development of traditional computers has moved on into areas those first pioneers could only have dreamed about.It was forward and then up, and beyond that, too.From the 1950s to the watershed period of the mid-1970s, the so-called ‘powerful computers’ were exclusively in the hands of computer scientists and other specialists at esteemed places of higher learning like MIT, Stanford and Oxford. Then, a miracle occurred: computers become smaller and cheaper. Machines like the Apple II and Commodore’s PET democratized the use of computers, making them available to everyone.Hooray.MindblowingThese days, ‘quantum’ is a byword for where we are going, although the technology is still in its genesis. To understand quantum computers and what — if our minds and design applications get to grips with them — they can do for us is mindblowing. Quantum theory, fathered by the geniuses of our age Max Planck and Albert Einstein amongst others, is for many a subject so difficult to understand, so sheathed in intellectual rhetoric that it frightens the life out of many if only because of its sheer incomprehensibility. NASA, along with tech giants IBM and Google, is pumping its unlimited tech dollars into the quest to understand and use quantum technology to build a new type of computer. In China, too, things are gaining momentum in this sphere.A quantum race could very much be on the cards.With governments and tech companies leading the way, there is no doubt that in the years and decades to come the world of quantum computers will, like their classic brethren, become more ‘the norm’. There are some computer scientists and quantum physicists out there who believe the practical use of this technology is closer to realization than we think.Just watch this space.QuantumordinaryThe binary system of 1or 0 is the operational modality of classical computation, which in its essence is based on how the human mind operates. In stark contrast, quantum computers are modeled on the laws according to the universe. In this system, all the operational complexities of the classical model are included yet with the incorporation of the laws of quantum physics, too.The binary system, the model for classical computers. Source: FacebookIn quantum computing, the ‘qubit’ has replaced the’ bit’, which is used in the binary system of the classical model. The result of using qubits instead of bits is the same regarding the number of qubits you get by adding to the chain. What makes qubits — and the quantum model extraordinary (or should I say quantumordinary) — is the fact that two radical events occur to the qubits that do not transpire in classical computer models, the phenomena of ‘superposition’ and ‘entanglement’. Here, the laws of physics take a very spooky and irregular path. In plain English, and without decorating the description with any scientific accouterments, in the quantum model superposition, or ‘superposition of states’, means the qubit, as opposed to a bit, can be both 1 and 0 at the same time, rather than in one state of a bit. Subsequently, entanglement is the event when two qubits get ‘entangled’ with each other, regardless of spatial parity between the two phenomena (which are not really phenomena but a unified phenomenon).Qubits Entangled — don’t worry, I don’t understand it either. 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And if so, will they be as useful as classical computers have been for humanity over the last five or so decades?The New PC?One of the key areas computer scientists believe quantum computers will be useful in the future is in cryptography. Currently, classical computers — as is the case with cryptocurrency and the underlying technology of how it operates, blockchain — are unable to break the codes. Scientists and cryptocurrency advocates fear, and quite rightly so, that the introduction and widespread use of quantum computers and the power they have will make blockchains secured by classical computer cryptographic operations breakable, rendering them useless in a security sense. This, in turn, is motivating researchers to develop encryption methods (based on the idea of quantum blockchains, a simple case of like for like) that oppose the threat of quantum attacks and other virtual malefactions.As well as in cryptocurrency, specialists also surmise quantum computers will have their uses in medicine, the future applications of neural networks for artificial intelligence and other areas of science.Yet what about us? Will they affect our lives? Will we, like with classical computer models, be able to use them?For EverybodyThe answer to the last question, at least, can be answered. In 2016 the tech giant IBM created the Q Experience quantum computer which possesses two 5-qubit processors and a 16-qubit processor as well as being open access and free to use for everybody. Measuring it up to what they will probably be able to do and how they will look in the years to come, it isn’t very powerful, but this device, based in the cloud, can be used by anyone with the ability to construct and run quantum circuits. Not bad, methinks.Google, however — in a prime example of oneupmanship — has created its own quantum computer, called Bristlecone, a 72-qubit gate-based superconducting system that beats IBM by a mile and also confounds the specialists who believed 50 qubits was entering ‘quantum supremacy’.Even more recently is the case of IonQ, a quantum computing hardware and software company based in Maryland, which late in 2018 claimed it is developing a quantum computer which could go up to 160 qubits, smashing current claims on processor capacity.Whatever happens, it’s surely a wild west scenario.So, mirroring the late 70s and early 1980s, when the ZX Spectrum and Amstrad 64 became the norm in people’s homes, maybe soon enough — or is that a pipe dream — quantum computers will be in everybody’s living rooms or some other conveniently located place.ZX Spectrum, a classic PC. Source: WikipediaThe age of quantum computers has begun. As we shift from the classical model to this new, quantum model, only time will tell how we will use them.But whatever it is, I hope it is for the moral side of creative.Will Quantum Computers Ever Replace The Humble PC in Our Living Rooms? was originally published in Hacker Noon on Medium, where people are continuing the conversation by highlighting and responding to this story.

Bitcoin [BTC] is easier to be made quantum-secure than Monero, says Blockstream researcher

The cryptocurrency community has been quite vocal about potential attacks by quantum computers in the future. According to many theories, quantum computing will become so powerful that it might eventually break and decode modern-day encrypted algorithm. Even as Bitcoin programmer, Jimmy Song, dismissed claims that quantum computing could harm digital assets, Andrew Poelstra, when asked about Monero not being fully secure and vulnerable to different kinds of attacks, admitted, “The only threat we are aware of to the elliptic curve discrete logarithm problem for the curves that we’re all using there are indeed quantum computers” The question, according to him, is whether there will be a quantum computer that is large enough in terms of qubits to decode the logarithm. The researcher however, claimed that it is not an immediate cause of concern. He also admitted that things like these take time to develop and that there should be an effort to develop systems that are resilient to future attacks. He further stated that for Bitcoin, the situation would not be any better. Poelstra revealed that in practice, around two-thirds of all public keys that control coins in the Bitcoin network are currently exposed and are known to people. So, a powerful quantum computer in the future would seamlessly “steal all those points.” With the king coin however, the only simpler thing would be the transition plan if quantum computers actually happen to breach the network. The transition, in this case, would be simpler because all it requires is to replace the digital signature algorithm in order to be quantum-resistant. But in case of the privacy coin, Monero, the replacement process would be complex as it includes replacing the Ring CT [Confidential Transactions], which is a vital part of the network. The post Bitcoin [BTC] is easier to be made quantum-secure than Monero, says Blockstream researcher appeared first on AMBCrypto.

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