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Google Builds Circuit to Solve One of Quantum Computing's Biggest Problems (ieee.org)
Researchers at Google, the University of Massachusetts at Amherst, and the University of California Santa Barbara has solved one of the biggest limitations with quantum computing: all the control and readout circuits of quantum computer systems must be at room temperature, while their superconducting qubits live in a cryogenic enclosure at less than 1 kelvin. "For today's sub-100-qubit systems, there's enough space for specialized RF cabling to come in and out of the enclosure," reports IEEE Spectrum. "But to scale up to the million-qubit systems needed to do really cool stuff, there just won't be enough room."
At the IEEE International Solid-State Circuits Conference in San Francisco last month, the researchers reported making a key control circuit in CMOS that will work at cryogenic temperatures. They described it as "a high-performance, low-power pulse modulator needed to program the qubits." From the report: "The current approach is OK for now," says Joseph Bardin, a University of Massachusetts at Amherst associate professor of electrical and computer engineering who designed the IC while on sabbatical at Google. "But it's not scalable to a million qubits." For Google's 72-qubit quantum processor there are already 168 coaxial cables going into the refrigerator and connecting to the 10-millikelvin quantum processor. The pulse modulator IC Bardin worked on is used to encode quantum states on a qubit in order to execute a program. Quantum computers get their parallelizing power because qubits don't have to be just 0 or 1, like the bits in an ordinary computer. Instead, they can be a mix of those states. The pulse modulator uses a specific set of RF frequencies to produce that mix.
"The biggest challenge is heat dissipation," explains Bardin. The qubits are at 10 millikelvins, but the control circuits, which necessarily throw off heat, can't be held that low. The researchers aimed for 4 K for the control IC. "However, at 4 K, thermodynamics limits the efficiency of cooling. The best you're going to get is about 1 percent efficiency. In practice it's worse." So the power dissipated by the electronics per qubit had to be only in the milliwatt range. That power constraint had to be balanced with the need for control accuracy, Bardin says. This was complicated by how differently CMOS transistors behave at 4 k, which is a more than 200 degrees below what silicon foundries' simulation models can deal with. Bardin and the Google team managed to design the IC in a way that compensates for these problems and achieves the balance between power consumption and performance. The resulting IC consumed less than 2 mW, yet it was able to put a qubit through its paces in testing.
At the IEEE International Solid-State Circuits Conference in San Francisco last month, the researchers reported making a key control circuit in CMOS that will work at cryogenic temperatures. They described it as "a high-performance, low-power pulse modulator needed to program the qubits." From the report: "The current approach is OK for now," says Joseph Bardin, a University of Massachusetts at Amherst associate professor of electrical and computer engineering who designed the IC while on sabbatical at Google. "But it's not scalable to a million qubits." For Google's 72-qubit quantum processor there are already 168 coaxial cables going into the refrigerator and connecting to the 10-millikelvin quantum processor. The pulse modulator IC Bardin worked on is used to encode quantum states on a qubit in order to execute a program. Quantum computers get their parallelizing power because qubits don't have to be just 0 or 1, like the bits in an ordinary computer. Instead, they can be a mix of those states. The pulse modulator uses a specific set of RF frequencies to produce that mix.
"The biggest challenge is heat dissipation," explains Bardin. The qubits are at 10 millikelvins, but the control circuits, which necessarily throw off heat, can't be held that low. The researchers aimed for 4 K for the control IC. "However, at 4 K, thermodynamics limits the efficiency of cooling. The best you're going to get is about 1 percent efficiency. In practice it's worse." So the power dissipated by the electronics per qubit had to be only in the milliwatt range. That power constraint had to be balanced with the need for control accuracy, Bardin says. This was complicated by how differently CMOS transistors behave at 4 k, which is a more than 200 degrees below what silicon foundries' simulation models can deal with. Bardin and the Google team managed to design the IC in a way that compensates for these problems and achieves the balance between power consumption and performance. The resulting IC consumed less than 2 mW, yet it was able to put a qubit through its paces in testing.
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=BeauHD=
s e ni o r z 2 0 1 9
I have no idea what was accomplished, but it sounded darn impressive.
21.1 Whogivesafucks, it's still fantasy 60% accurate quantum snake oil. Wake me in 50 years when the polaroid begins to fade.
Naw, just came here to post this.
Happiness in intelligent people is the rarest thing I know.
Ernest Hemingway
According to one of the founders of quantum computing. The complexity explodes requiring infinite energy.
Sooner or later, quantum computing will join cold fusion as an illegitimate science.
In the mean time, one would assume that it isn't already in that camp because it is a fund raising buzzword or some such thing.
Or perhaps a way to fleece funds from the US government, who love spending money on make believe technologies.
If you're dealing with the lowest of temperatures then it's a perfect environment for superconductive materials. My question is why wouldn't they build a superconductive circuit?
Anons need not reply. Questions end with a question mark.
> Quantum computers get their parallelizing power because qubits don't have to be just 0 or 1, like the bits in an ordinary computer.
Not at all. This is a trivial property a quantum computer shares with any analog computer (quantum or not). They get their power from the fact, that the state spaces of interacting quantum subsystems combine with the tensor product (dimensions multiply) and not with the outer product (dimensions add), like classical systems do.
One qubit (ignoring phase and normalization) can be described by 2 complex numbers. 10 isolated qubits which only interact by classical signals form a product state which can be described by 2*10 = 20 complex numbers. But the state of 10 qubits entangled qubits (i.e. qubits which have interacted quantum mechanically in a non trivial way) needs 2^10 = 1024 complex numbers.
A measurement still only gives 10 classical bits of information, however, so the art is to manipulate the state such that interesting values get high and "dull" values get low probability.
ignatius
Can it even play Crysis?
Is there anywhere an explanation of how they work? And I mean explanation, not what a qubit is etc. I have seen Susskinds theoretical minimum. What I want to know, how it was possible to construct a device to operate so much faster than conventional processors and be able to get so many outputs simultaneously.
I'm 99% sure many of you will dislike this post, but for me, true quantum machines, like the brain, evolve in a way that is beyond the realm of "control." Sure, go ahead and pioneer this very staticly controlled quantum machine a la classic computing theory; but I believe the real power lies in evolving networks that respond to quantum signals in ways that are less predictable. How would this look and what would it do, I can't give any specifics, but if we really want to play God, I think this is the way to do it.