New silicon structure opens the gate to quantum computers
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Re: New silicon structure opens the gate to quantum computers
#2Anybody who can read the actual PDF -- is this at room temp and no large magnetic field? Those two things seem to be the big stumbling blocks for these types of quantum computers..
Re: New silicon structure opens the gate to quantum computers
#3Re: New silicon structure opens the gate to quantum computers
#4Anybody who can read the actual PDF -- is this at room temp and no large magnetic field? Those two things seem to be the big stumbling blocks for these types of quantum computers..
Paper is linked below and way out of my depth but the only mention of temperature I could find was 150 mK so I'd assume this is not done at room temperature.
Re: New silicon structure opens the gate to quantum computers
#5Anybody who can read the actual PDF -- is this at room temp and no large magnetic field? Those two things seem to be the big stumbling blocks for these types of quantum computers..
Yep, still a major issue. This was run at 0.15 kelvin (-273c/-459.4f) and they'd like to get it colder:
In these experiments, the electron temperature accounts for 10% of the reduction in our visibility, and spin relaxation accounts for the remaining 5-10%. In our experiment we readout the qubits sequentially, reading the left qubit first. Relaxation of the right qubit during the readout of the left qubit is what leads to the asymmetry of the expected visibilities. Relaxation contributions to the readout fidelity can be mitigated by using a faster readout technique such as RF reflectometry or by incorporating a cold amplifier into the readout circuit (9, 10). Further improvements can be made by reducing the electron temperature or using cavity-based measurement approaches (11).
Re: New silicon structure opens the gate to quantum computers
#6I haven't touched this stuff in a while so take this with a grain of salt.
This is good progress since it's about an order of magnitude faster for operations than previously constructed CNOT gates, however it still has many caveats for a semiconducter-like leap towards real quantum computers:
a) Low temperature bound for the level of fidelity they want
b) Doesn't allow us to engineer quantum chips of more qubits efficiently since the decoherence between quantum dots is still a major issue.
c) The science journalism title is a bit misleading. While this happens in a silicon structure there is nothing new about it, what's new is that they managed to use the driving resonance to control the dephasing during the gate operation.
Re: New silicon structure opens the gate to quantum computers
#7FYI: This is for a very different substrate (quantum dots, which are basically individual electrons trapped in special silicon defects) compared to the substrates that have seen more attention for quantum computing (superconducting circuits and trapped ions). They are behind in terms of raw qubit counts -- which are not that meaningful -- and in terms of their overall abilities, but they hope to catch up by building higher quality components that cross the fault-tolerant threshold first.
If, like me, you don't already know a lot about quantum computing experiments, this article shouldn't interest you. At best, this is a small step of many thousands that will be taken on the way building a working computer.
Re: New silicon structure opens the gate to quantum computers
#8I know nothing about this stuff but this caught my eye:
“The challenge is that it’s very difficult to build artificial structures small enough to trap and control single electrons without destroying their long storage times,” said David Zajac, a graduate student in physics at Princeton and first-author on the study. “This is the first demonstration of entanglement between two electron spins in silicon, a material known for providing one of the cleanest environments for electron spin states.”
Electrides like Calcium Aluminate Electride can readily trap individual electrons. And it is stable at room temperatures.
Re: New silicon structure opens the gate to quantum computers
#9I did graduate research in an area of experimental physics that was quite close to state of the art quantum computing research. It was very exciting, but all the research was pretty much in extreme conditions that aren't really usable for a realistic computing device (ultra-high vacuum, nanokelvin temperatures, high magnetic fields or laser trap confinement, etc.). From the looks of it this paper is in the same vein. Good progress, but the gate isn't quite "open" yet.
Re: New silicon structure opens the gate to quantum computers
#10My biggest pet peeve about quantum computing is that no one can answer me the question of "what can quantum computing do for me?".
The answer I hear is that it helps solve the traveling salesman in record time, and that's all great and everything, but how will quantum computing be able to do things such as decrease the time it takes to train a RNN, or look up data in a database?