drkevorkian
Joined 17 years ago
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Recent submissions
Comment · 1 year ago
Comment · 1 year ago
There are two points. You got the first one, which is controllability. The components are controllable and programmable. But second it's important to appreciate the difference between simulating 10^23 classical billiard balls with a computer (very hard, C * 10^23 work for some C) and simulating 10^23 quantum mechanical atoms (C * d^(10^23) work for some C and some d). Those numbers are very different.
Comment · 1 year ago
No, not quite, it's about the error-per-gate. RCS has very loose requirements on the error per gate, since all they need is enough gates to build up some arbitrary entangled state (a hundred or so gates on this system). Other algorithms have very tight requirements on the error-per-gate, since they must perform a very long series of operations without error.
Comment · 1 year ago
It's different from your hourglass in that the computer is controllable. Each sampled random circuit requires choosing all of the operations that the computer will perform. You have no control over what operation the hourglass does.
It won't be factoring large numbers yet because that computation requires the ability to perform millions of operations on thousands of qubits without any errors. You need very good error correction to do that, but luckily that's the other thing they demonstrated. Only when they do error correction, they are basically combining their system down into one effective qubit. They'll need to scale by several orders of magnitude to have hundreds of error corrected qubits to do factoring.
Comment · 2 years ago
The ones dropped into the macerator are the lucky ones. The ones who live suffer for their short lives, until their economic utility curve crosses a threshold value and they are also slaughtered.
Comment · 2 years ago
I agree with the premise that "nobody deserves to be a millionaire" (although maybe with inflation we should say deca-millionaire), but a hard cap seems like a crude tool with many potential downsides. A UBI would be a better tool for raising living standards, and a progressive wealth tax would be a better guard against hereditary fortunes, without removing the incentives for high earners to continue working.
Comment · 2 years ago
As much as I hate to admit it, their pushback on account sharing finally stopped me from leeching on my relatives account.
Comment · 2 years ago
Habitable? There is plenty of water for it to be habitable, residential use is a drop in the bucket compared with agricultural use. Without a technological solution, we'll have to scale back agriculture, but that's not a regional problem, since the market for food is an international one.
Comment · 2 years ago
Not sure what you're saying here, YBCO and related materials become superconducting with liquid nitrogen temperatures
Comment · 2 years ago
Yes, good point (apologies to the Lukin group). That's an interesting proposal, but it seems from a cursory read that you would need still need very many physical qubits to approach that asymptotic rate, and also you would be forced to take a very large slow down due to serializing all of your logical operations through a smaller set of conventionally encoded logical qubits. That said, I'm not current on SOA LDPC QEC proposals, so I'll moderate my claim a bit to "the first actually useful logical qubits will almost certainly have an encoding rate lower than 1/5".
Comment · 2 years ago
Don't get me wrong, their (QuEra's) demonstration is incredibly impressive, but it seems you've been misled by inconsistent nomenclature around the phrase "logical qubit". They've demonstrated a 5/1 encoding scheme, yes, but that scheme is not anywhere close to being sufficiently redundant to allow for deep quantum circuits. When people talk about needing 1000 physical qubits, they mean to make a logical qubit with sufficiently low error rate to run interesting algorithms. In the QuEra device, when they say they "made 48 logical qubits out of 240 physical qubits", they simply meant that they used an encoding, and made no claim about the error rate on those qubits being low enough. There is no hope (that I know of) for a 5-1 encoding scheme to make error rates low enough. The QuEra device would just as well need many more physical qubits per logical qubit.
Comment · 3 years ago
This would be a backwards incompatible change that would cause a lot of issues. For instance, you are not allowed to compare naive and non-naive datetimes, so for instance, `utcnow() > datetime(2023, 11, 19)` would work before, but break following your change.
Comment · 12 years ago
Two counterpoints:
1) What you've written, where H is independent of t is reducible to just the Eigenvalue problem for H. Certainly better understood than fluid dynamics. Even with time-dependent hamiltonians we have decent tools for talking about the solutions (Dyson series).
2) Of course for certain values of H, (esp. in continuous space) you can contrive ways of making the eigenvalue problem hard, but you don't have to go as far as quantum mechanics to find difficulty. Just take three bodies under newton's gravitation.
Yes, the quantum n-body problem is exponentially harder in n, but that's a fundamentally different type of "hardness" than the hardness of Navier-Stokes.
Comment · 12 years ago
This is a cool demo, but I'm afraid this is the wrong pedagogical approach to understanding quantum computing.
The representation of the quantum state as a bar chart is difficult to interpret and provides little intuition. The fact is, visualizing vectors in high-dimensional spaces is hard, much less vectors in high-dimensional complex spaces. Bra-ket notation is pretty much the best thing we have right now.
But more generally, "Quantum programming" will almost certainly look nothing like this. This is like programming a classical computer by describing a boolean circuit. It's an extremely useful model for researchers working with actual hardware, but there's a reason we currently program with lambda calculi, not NAND gates. Understanding how to capture the possibilities of quantum circuits in a higher-level language is an open problem. Many interesting attempts have been made at solving it, but none convincingly in my opinion.
Comment · 13 years ago
for word, count in Counter(open('test.txt').read().lower().split()).most_common():
print word, count
You simply do not need to believe this. The universe doesn't need to be "stored" somewhere.
> Quantum Computing is firmly based on pretending that this isn't how it is, that somehow you can squeeze 2^n bits of information out of a system with 'n' parts to it.
Quantum computing does not believe this. It is a theorem that you can only get n bits out of n qubits, and quantum computing speedups do not rely otherwise.
Noise is hard, but error correction is a mathematically sound response.