Google Builds Circuit to Solve One of Quantum Computing's Biggest Problems (ieee.org) 42
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.
Re: BeauHD is reatardeder (Score:1)
Researchers at.... has solved
Mixing singular with plural are truly the mark of one great editors.
Impressive (Score:2)
I have no idea what was accomplished, but it sounded darn impressive.
Re:Impressive (Score:5, Interesting)
Ordinarily, the electronics to set the state of a qubit are external to the cryogenic chamber that houses the device, and the state is fed in through coaxial cables. They made a version that can reside inside the cryogenic chamber.
External programming wasn't ever going to scale up. Even if they managed to get it down to 1 cable per qubit, that wasn't going to scale either.
Since I mostly follow the software side of quantum computing, I was expecting something entirely different. There is a quantum algorithm that can "solve" any problem that can be presented as a reversible circuit. What this article is talking about isn't a circuit in that sense, and it isn't a problem in that sense, and it hasn't been solved in that sense.
In my mind, this is more of a "device" which is in line with the terminology we use for other specialized CMOS structures. And it is more like "overcoming an engineering hurdle" than "solving one of QC's biggest problems".
But still quite impressive.
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In my mind, this is more of a "device" which is in line with the terminology we use for other specialized CMOS structures. And it is more like "overcoming an engineering hurdle" than "solving one of QC's biggest problems".
But still quite impressive.
Indeed. The biggest hurdle is that entanglement scales extremely badly. From available evidence (scaling over several decades), even an exponential increase in effort for each qbit added is plausible. That would mean that QC's will not get much larger than they are today and will never even reach the power of conventional computers. That they talk about millions of qbits is just hubris.
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Indeed. The biggest hurdle is that entanglement scales extremely badly. From available evidence (scaling over several decades), even an exponential increase in effort for each qbit added is plausible. That would mean that QC's will not get much larger than they are today and will never even reach the power of conventional computers. That they talk about millions of qbits is just hubris.
This research actually addresses that exact problem. Having a bunch of coax cables hanging off the device is a major potential source of noise.
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No, it does not. The cables are an _additional_ problem to scaling that comes in only with doing computations.
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You should not guess, you are terrible at it. Buying Bitcoin is a terrible idea, but that has nothing to do with using QCs to factor numbers in the required sizes. That will not happen anytime soon.
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Sorry if I misjudged you, it's typically the cryptoshills screaming that quantum computing won't happen as if their cries will make it that way.
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Complete nonsense, spouted by uninformed morons and those greedy for funding and not above lying. There is no linear trend in qbits either, as soon as you require that all-critical entanglement being stable under computations.
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Not entangled ones. Those are worthless.
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It seems obvious that only Ceiling Cat contains enough entropy in a small enough space to entangle millions of qubits.
So you'd only be able to run it one or two times, most likely, before the cat is consumed, and how do you replace it? It would take years.
Hmmmm (Score:3)
Naw, just came here to post this. [youtu.be]
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assumption: 1. a thing that is accepted as true or as certain to happen, without proof.
I'm with you. Opinions should be derived not from personal feedback from environment experience, but from situations you believe are quite unlikely to occur, yet provably so.
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...as I believe it is below the standards of this website.
Whew. Your bluff was spot on until right then.
Quantum computings biggest problem: impossibility (Score:1)
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.
Why not superconductors? (Score:2)
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?
Not the source of the speedup (Score:3)
> 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
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Reasonable explanation IMO.
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It's not about storing. Storing means that something can be retrieved. In that sense a qubit can store 2 classical bits (using superdense coding), the decoding procedure uses a additional "fresh" qubit and there is afaik no exponential buildup - so nothing to write home about.
Normalization reduces the degrees of freedom by one, the irrelevance of the overall phase also. So total number of real numbers is reduced by two. The state of n qubits can therefor be described by 2*2^n-2 real numbers (instead of 2*2^
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But (Score:1)
Can it even play Crysis?
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Can it even play Cryosis?
FTFY