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All current programmable quantum processors are made from unicorn hairs and fairy dust. The current state of the art is trying to prove that the thing did some

All current programmable quantum processors are made from unicorn hairs and fairy dust. The current state of the art is trying to prove that the thing did something quantum. Programmability is at best swapping some wires around to change that something.

Strilanc 5y ago
Programming current quantum computers does not require swapping wires around. You can go to https://quantum-computing.ibm.com https://quantum-computing.ibm.com right now, drag some operations around in an editor, and have their quantum computer run those operations. No one is madly dashing around changing wires when you do that.
- westurner 5y ago
  That was how they did it back in the old days though. Q: "Ask HN: What's the Equivalent of 'Hello, World' for a Quantum Computer?" https://news.ycombinator.com/item?id=22707580 https://news.ycombinator.com/item?id=22707580 [ IBM Qiskit, Microsoft Q#, Google TFQ TensorFlow Quantum, Google Cirq ([NumFOCUS,] SymPy) ] - https://www.tensorflow.org/quantum/tutorials/hello_many_worlds https://www.tensorflow.org/quantum/tutorials/hello_many_worl... A: Set a register to zero and see how many times it reads as zero: A) in the local software simulator; and B) with just one modern day qubit register.
- NohatCoder 5y ago
  All the offered "quantum computers" are suspiciously easily simulated on a normal PC.
  - klyrs 5y ago
    Not if you try to simulate the actual device under test, and not an idealized version of what it isn't. Nothing suspicious about it, they're small and noisy. Scalability is extremely hard for quantum computers, and there's distinct tradeoffs that need to be made in their engineering. As far as I know, nobody in the industry is making absurd claims about their current offerings. That said, some claims of projected growth I've seen appear to be batshit. And, I believe that you're wrong: Google's quantum supremacy result appears to be genuine, and IBM's refutation was, essentially, "we can use a ginormous supercomputer to match that" -- not your ordinary desktop.
  - reikonomusha 5y ago
    46 qubits of a perfectly ideal quantum computer require a petabyte of RAM to simulate, and about 10 quadrillion—if not more—arithmetic instructions to perform a single quantum instruction.
reikonomusha 5y ago
This is false. Quantum computers are not programmed like telephone switch boards. They're programmed typically by sending signal pulses (of RF, DC, or light) of the right shape at the right time to physical elements and they react. It really is programming. Moreover, it's remarkably easy to see that the machines—universal gate-based machines—are doing something quantum. What's not easy to see is if they'll ever break away from their scaling challenges and become useful, large scale machines.
- dekhn 5y ago
  Well, NMR has been doing that for quite some time but nobody considers it "computing". Realistically, you're encoding a problem within a physical system by perturbing its energy levels, letting them evolve, and then doing readout. This works because computation is universal.
  - reikonomusha 5y ago
    Again, no. Maybe you're thinking about adiabatic quantum computation, something popularized by D-Wave. But most people in the industry don't call their machines "(universal) computers," but rather "quantum annealers." This is not the same as universal, gate-based computation, which does take an actual program containing instructions, and executes those instructions more-or-less sequentially, just as any computer programmer would expect. The state of the system begins with what is essentially equivalent to a large array of 0's, and you manipulate it accordingly, without resorting to evolution as your primary computational means of marching forward. In fact, left alone, these computers are designed to remain static, like an ordinary computer. (However, they still couple with the environment and decohere, which is one of the major challenges we, as humanity, face in building a useful quantum computer.) This is what Rigetti, IBM, Google, HRL, Amazon, IonQ, ColdQuanta, etc. are doing. They use superconducting transmon qubits, ion qubits, neutral atom qubits, or silicon quantum dot qubits. (There are other companies and qubit technologies still.)
    - dekhn 5y ago
      Hey, um, I think I do know what I'm talking about :). You can see more of this historical side effort, which didn't pan out for a number of reasons: https://en.wikipedia.org/wiki/Nuclear_magnetic_resonance_quantum_computer https://en.wikipedia.org/wiki/Nuclear_magnetic_resonance_qua... A 7 qubit QC NMR was implemented in 2001. All these systems are just evolution of spin systems or other similar systems. The big difference with an NMR quantum computer is that it manipulates ensembles of spins. The comment about universality of computing is that many physical processes can be used to compute things. I didn't say that qcs were universal computers. Please try to read what i'm writing more carefully.

Strilanc 5y ago

Programming current quantum computers does not require swapping wires around. You can go to https://quantum-computing.ibm.com https://quantum-computing.ibm.com right now, drag some operations around in an editor, and have their quantum computer run those operations. No one is madly dashing around changing wires when you do that.

westurner 5y ago
That was how they did it back in the old days though. Q: "Ask HN: What's the Equivalent of 'Hello, World' for a Quantum Computer?" https://news.ycombinator.com/item?id=22707580 https://news.ycombinator.com/item?id=22707580 [ IBM Qiskit, Microsoft Q#, Google TFQ TensorFlow Quantum, Google Cirq ([NumFOCUS,] SymPy) ] - https://www.tensorflow.org/quantum/tutorials/hello_many_worlds https://www.tensorflow.org/quantum/tutorials/hello_many_worl... A: Set a register to zero and see how many times it reads as zero: A) in the local software simulator; and B) with just one modern day qubit register.
NohatCoder 5y ago
All the offered "quantum computers" are suspiciously easily simulated on a normal PC.
- klyrs 5y ago
  Not if you try to simulate the actual device under test, and not an idealized version of what it isn't. Nothing suspicious about it, they're small and noisy. Scalability is extremely hard for quantum computers, and there's distinct tradeoffs that need to be made in their engineering. As far as I know, nobody in the industry is making absurd claims about their current offerings. That said, some claims of projected growth I've seen appear to be batshit. And, I believe that you're wrong: Google's quantum supremacy result appears to be genuine, and IBM's refutation was, essentially, "we can use a ginormous supercomputer to match that" -- not your ordinary desktop.
- reikonomusha 5y ago
  46 qubits of a perfectly ideal quantum computer require a petabyte of RAM to simulate, and about 10 quadrillion—if not more—arithmetic instructions to perform a single quantum instruction.

reikonomusha 5y ago

This is false. Quantum computers are not programmed like telephone switch boards. They're programmed typically by sending signal pulses (of RF, DC, or light) of the right shape at the right time to physical elements and they react. It really is programming. Moreover, it's remarkably easy to see that the machines—universal gate-based machines—are doing something quantum. What's not easy to see is if they'll ever break away from their scaling challenges and become useful, large scale machines.

dekhn 5y ago
Well, NMR has been doing that for quite some time but nobody considers it "computing". Realistically, you're encoding a problem within a physical system by perturbing its energy levels, letting them evolve, and then doing readout. This works because computation is universal.
- reikonomusha 5y ago
  Again, no. Maybe you're thinking about adiabatic quantum computation, something popularized by D-Wave. But most people in the industry don't call their machines "(universal) computers," but rather "quantum annealers." This is not the same as universal, gate-based computation, which does take an actual program containing instructions, and executes those instructions more-or-less sequentially, just as any computer programmer would expect. The state of the system begins with what is essentially equivalent to a large array of 0's, and you manipulate it accordingly, without resorting to evolution as your primary computational means of marching forward. In fact, left alone, these computers are designed to remain static, like an ordinary computer. (However, they still couple with the environment and decohere, which is one of the major challenges we, as humanity, face in building a useful quantum computer.) This is what Rigetti, IBM, Google, HRL, Amazon, IonQ, ColdQuanta, etc. are doing. They use superconducting transmon qubits, ion qubits, neutral atom qubits, or silicon quantum dot qubits. (There are other companies and qubit technologies still.)
  - dekhn 5y ago
    Hey, um, I think I do know what I'm talking about :). You can see more of this historical side effort, which didn't pan out for a number of reasons: https://en.wikipedia.org/wiki/Nuclear_magnetic_resonance_quantum_computer https://en.wikipedia.org/wiki/Nuclear_magnetic_resonance_qua... A 7 qubit QC NMR was implemented in 2001. All these systems are just evolution of spin systems or other similar systems. The big difference with an NMR quantum computer is that it manipulates ensembles of spins. The comment about universality of computing is that many physical processes can be used to compute things. I didn't say that qcs were universal computers. Please try to read what i'm writing more carefully.