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Forget about quantum computing at scale: has anyone actually developed a functional quantum device that unequivocally proves that it's both viable and that it s

Forget about quantum computing at scale: has anyone actually developed a functional quantum device that unequivocally proves that it's both viable and that it solves a problem faster than conventional physics can explain? To the best of my knowledge, the answer is no. It's premature to invest heavily in something this speculative. I'm all for investing in research and science for the sake of science, but we didn't invest billions in going to the moon before we knew that rockets worked.

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adrianN 8y ago
We have demonstrated systems with a handful of quantum bits that worked as expected. There is a tremendous amount of work left before anything practical can be build, afaik.
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sp332 8y ago
We're really close. Actually Intel announced a 49-qubit quantum computer which would have beaten existing classical platforms, but just after that, another team at IBM [edit: not Intel] made an algorithmic breakthrough and simulated 56 qubits on a classical supercomputer. https://en.wikipedia.org/wiki/Quantum_supremacy https://en.wikipedia.org/wiki/Quantum_supremacy
- stcredzero 8y ago
  Can this 56 qubit computer break DES faster than conventional computers? Could it break an arbitrary 56 bit block cipher faster than conventional computers? Or is it limited in a way which limits it to specific problems? I suspect the answer is the latter.
  - sp332 8y ago
    Well it's certainly not as fast as a real quantum computer would be. The advantage it has over similar-scale real quantum computers is that it exists.
  - 6nf 8y ago
    No, 56 qubits is still much too small to break any useful encryption. And your second point is true too - these are not general purpose quantum computers and can't run arbitrary quantum algorithms.
  - caymanjim 8y ago
    I'm not expecting quantum computers to actually do anything faster than conventional computers for many years, and that's fine; making things incrementally better is usually much easier than making them work in the first place. People have been simulating quantum circuits as proof-of-concept for quantum algorithms, and D-Wave has a "quantum annealing" machine (although a preliminary glance suggests there's skepticism about whether that involves any provable quantum effect), and there are frequent reports about pushing the limits of entangled qubit count, but I'm wondering if anyone's actually made a quantum device that solves even a specific problem faster than non-quantum physics would allow (hence my original comment along those lines), rather than faster than conventional hardware (which could take years or decades to match).
jazzyjackson 8y ago
To your point, we invested billions in rockets before we knew we would go to the moon! Of course rockets were useful for moving bombs quickly in the meantime. Quantum computers won't be faster at solving conventional problems, but they will be useful for simulating quantum behaviors related to chemistry and cosmology. Maybe we'll make sense of dark matter, who knows? I'm in the camp that we'll develop totally new problems to solve that didn't fit the domain of digital computers.
abdullahkhalids 8y ago
From a singular technology perspective, indeed it seems like investing a lot of money into a hypothetical device. However, there are many other factors you have to consider. 1. Quantum computing is a cryptographic arms race at the moment. One country can choose not the invest in it, but assuming QCs work, whichever country makes one first, is going to win big time. In a way, its a national security issue. Nobody wants to be left behind. Funding levels have to reflect this. 2. Many different architectures for QCs are being researched on, and in each area we have made tremendous advancements in new techniques of quantum-level-system control and new ways of nano scale manufacturing etc. The feedback alone from these advancements will enrich and enable many other areas of science and technology. For instance, the development of photonic quantum computation also advances the development of optical classical computer as the basic architecture is very similar. 3. Many physicists like myself don't care too much about actually building quantum computers, though it would be nice. Whether or not QCs are possible, just forcing ourselves to think about physical reality from a computational and information theoretic perspective has resulted in massive advancements in physics, a field which had pretty much stagnated since the 80s. The ideas generated from studying quantum information and computation have percolated into other areas of physics such as gravitation and the structure of spacetime. And its not sufficient to just think about QCs in the abstract. New ideas such as novel error correction codes are generated when physicists are forced to think about specific architectures and their limitations and/or real problems faced in the lab.

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adrianN 8y ago

We have demonstrated systems with a handful of quantum bits that worked as expected. There is a tremendous amount of work left before anything practical can be build, afaik.

deleted 8y ago

[deleted]

sp332 8y ago

We're really close. Actually Intel announced a 49-qubit quantum computer which would have beaten existing classical platforms, but just after that, another team at IBM [edit: not Intel] made an algorithmic breakthrough and simulated 56 qubits on a classical supercomputer. https://en.wikipedia.org/wiki/Quantum_supremacy https://en.wikipedia.org/wiki/Quantum_supremacy

stcredzero 8y ago
Can this 56 qubit computer break DES faster than conventional computers? Could it break an arbitrary 56 bit block cipher faster than conventional computers? Or is it limited in a way which limits it to specific problems? I suspect the answer is the latter.
- sp332 8y ago
  Well it's certainly not as fast as a real quantum computer would be. The advantage it has over similar-scale real quantum computers is that it exists.
- 6nf 8y ago
  No, 56 qubits is still much too small to break any useful encryption. And your second point is true too - these are not general purpose quantum computers and can't run arbitrary quantum algorithms.
- caymanjim 8y ago
  I'm not expecting quantum computers to actually do anything faster than conventional computers for many years, and that's fine; making things incrementally better is usually much easier than making them work in the first place. People have been simulating quantum circuits as proof-of-concept for quantum algorithms, and D-Wave has a "quantum annealing" machine (although a preliminary glance suggests there's skepticism about whether that involves any provable quantum effect), and there are frequent reports about pushing the limits of entangled qubit count, but I'm wondering if anyone's actually made a quantum device that solves even a specific problem faster than non-quantum physics would allow (hence my original comment along those lines), rather than faster than conventional hardware (which could take years or decades to match).

jazzyjackson 8y ago

To your point, we invested billions in rockets before we knew we would go to the moon! Of course rockets were useful for moving bombs quickly in the meantime. Quantum computers won't be faster at solving conventional problems, but they will be useful for simulating quantum behaviors related to chemistry and cosmology. Maybe we'll make sense of dark matter, who knows? I'm in the camp that we'll develop totally new problems to solve that didn't fit the domain of digital computers.

abdullahkhalids 8y ago

From a singular technology perspective, indeed it seems like investing a lot of money into a hypothetical device. However, there are many other factors you have to consider. 1. Quantum computing is a cryptographic arms race at the moment. One country can choose not the invest in it, but assuming QCs work, whichever country makes one first, is going to win big time. In a way, its a national security issue. Nobody wants to be left behind. Funding levels have to reflect this. 2. Many different architectures for QCs are being researched on, and in each area we have made tremendous advancements in new techniques of quantum-level-system control and new ways of nano scale manufacturing etc. The feedback alone from these advancements will enrich and enable many other areas of science and technology. For instance, the development of photonic quantum computation also advances the development of optical classical computer as the basic architecture is very similar. 3. Many physicists like myself don't care too much about actually building quantum computers, though it would be nice. Whether or not QCs are possible, just forcing ourselves to think about physical reality from a computational and information theoretic perspective has resulted in massive advancements in physics, a field which had pretty much stagnated since the 80s. The ideas generated from studying quantum information and computation have percolated into other areas of physics such as gravitation and the structure of spacetime. And its not sufficient to just think about QCs in the abstract. New ideas such as novel error correction codes are generated when physicists are forced to think about specific architectures and their limitations and/or real problems faced in the lab.