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So did the need for computers before the revolution started. It’s just a matter of time
I'm thinking of some kind of common computational work, with a clearly defined input and verified output, shown to be carried out at least an order of magnitude faster than our conventional computers.
Is there any demonstration of practical, usable QC yet? I'm thinking of some kind of common computational work, with a clearly defined input and verified output, shown to be carried out at least an order of magnitude faster than our conventional computers.
He's not wrong about the narrow algorithmic use cases (so far), but he's completely missing the utility for simulation of quantum phenomena (chemistry, microbiology, materials science). That use case alone completely justifies investing into them even if you don't care about advancing science.
Out of curiosity, how many qubits would you need to simulate the molecule of water?
Computer revolution was funded by demand in business, gaming and automation. It's the cash flow that funds long term R&D. Not potential benefit.
There is no such demand for quantum computers. Everyday problems have too small complexity for them to be useful even if algorithm exists.
I suspect that computational biochemistry will have funders from drug firms and companies doing materials science to keep funding the research for quantum computing, but the total sum will not be billions per year like it was in computer revolution.
I wonder if quantum computing is just a mirage that results from looking too much at the time complexity of quantum algorithms versus the cost in qubits, which are still wildly expensive. Maybe qubits will just never scale to the number of qubits needed to meaningfully outperform classical computers.
Let's assume decoherence won't be a problem.
How about a purely economic perspective. Something like the number of bits of DRAM you can get for the cost of a single qubit. Surely, for quantum computers to become usefulfrom a cost POV, this number needs to shrink, yes?
So it could then be interesting to graph this ratio over time and see where it's headed. My gut is that given the state of the art nature of QC, the cost of 1 qubit should be very high, whereas one bit of DRAM should be very low. Which mean 1 qubit is worth a crazy amount of DRAM.
Does anyone know if this has been analysed?
Normal computers would have suffered the same fate if they were only good for scientific calculations. Computer revolution was funded by demand in business, gaming and automation. It's the cash flow that funds long term R&D. Not potential benefit. There is no such demand for quantum computers. Everyday problems have too small complexity for them to be useful even if algorithm exists. I suspect that computational bioc…
Earlier quoted context omitted.
Out of curiosity, how many qubits would you need to simulate the molecule of water?
Can QC simulate that?
He's not wrong about the narrow algorithmic use cases (so far), but he's completely missing the utility for simulation of quantum phenomena (chemistry, microbiology, materials science). That use case alone completely justifies investing into them even if you don't care about advancing science.
Out of curiosity, how many qubits would you need to simulate the molecule of water?
Water has 8 electrons (which QC can treat exactly without any extra work) in a number of orbital. In general we need 2 qubits per orbital.
Most QC demonstrations so far were performed using so-called minimal basis sets, which have a small number of orbitals and thus give inaccurate results. A better approach would be to take a large orbital basis, do a classical relatively expensive Hartree-Fock calculation then use the orbitals from that to do the QC. This technique when done on classical computers is called MRCI (multi-reference configuration interaction) and is the gold standard in Quantum Chemistry.
So, provided we can pay the cost of doing a large orbital HF calculation (and we can do that for fairly large molecules), we can get pretty good result using n electrons in n orbitals MRCI. So production electronic calculations of water molecules would take about 16 qubits per molecule.
The more frustrating problem is that the number of electronic interaction terms is N^4 the number of orbitals so that we would very rapidly need extremely deep circuits which are not feasible without error correction (which involve using like 8 actual qubits for every calculation qubit). There are proposal to use plane wave basis sets (N^2 interactions) but then we need many more orbitals and thus many more qubits.
We are in practice very far from QC having a significant impact on real-life quantum chemistry. It's not at all clear that we'll ever be able to do QC on a molecule the size of a typical drug, let alone a protein.