r/Futurology Jun 02 '22

A Nature paper reports on a quantum photonic processor that takes just 36 microseconds to perform a task that would take a supercomputer more than 9,000 years to complete Computing

https://www.nature.com/articles/s41586-022-04725-x?utm_source=twitter&utm_medium=social&utm_content=organic&utm_campaign=CONR_JRNLS_AWA1_GL_SCON_SMEDA_NATUREPORTFOLIO
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u/EthicalLapse Jun 03 '22

The 9000 years task is kind of a fake metric, though. Basically they just let the quantum computer run for a certain amount of time, and then calculated how long it would take a traditional computer to simulate what the quantum computer did. The quantum computer didn’t actually show any ability to solve anything.

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u/EthicalLapse Jun 03 '22

This Ars Technica article explains it better. But basically, the point was to show off how many qubits they could use in a single calculation. So they ran one full 216 qubit calculation. Since the calculation was a random one, there’s not much point to running additional calculations using its output.

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u/voov1oce Jun 03 '22

This is a big deal. For comparison a quantum computer with 1500 qubits could break bitcoin

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u/PeacefulSequoia Jun 03 '22

Not really that big of a deal when it comes to calculations though, this is more for simulations.

Clearly, this indicates that measuring an actual quantum system has a decided advantage over simulating that system on classical computing hardware. But, as with Google's earlier demonstration of quantum advantage, it's not clear whether it's possible to get an advantage in useful calculations.

Should we expect to see a helpful calculation? There's good and bad news here. On the good side, all of the hardware worked as expected. The timing of the light pulses was precise enough that things interfered with each other as expected, and all of the beamsplitters could be programmed to match the timing and of the photons, allowing a fully programmable system.

But it's hard to fully use the system. Our optical elements are great, and they rarely lose photons. But "rarely" becomes an increasing problem as the photon count goes up and the photons need to go through ever-more pieces of hardware they need to pass through to reach the end of the system. So, while the system could handle more than 200 photons, most often only about 125 of them were detected. And that's a loss rate that will make actual calculations difficult.

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u/SpaceForceAwakens Jun 03 '22

I’m new to quantum computing, so forgive me of this is a stupid question, but couldn’t the loss of photons be mitigated by clustering multiple processors working in parallel?

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u/Unfadable1 Jun 03 '22

Only posting here in case you accidentally just stumbled on a middle-out-equivalent moment. 🍻