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If you are a researcher from another field that just wants to contract out the computation of a numerical solution to some chemistry problem infeasible on a cla

If you are a researcher from another field that just wants to contract out the computation of a numerical solution to some chemistry problem infeasible on a classical supercomputer, a million "physical" qubits is a fairly reasonable guestimate. If you are a quantum computation person developing near term applications, you probably would already start getting excited with a 100 (sufficiently long-lived) qubits. The "sufficiently long-lived" is the problematic part. Every lab has its own bespoke figure of merit (quantum volume, CLOPS, fidelities, etc). It is basically impossible to compare devices without being a researcher in the field for now. But at some point a novel drug or material will be developed thanks to a quantum computer and then we should really get excited about renting time on these devices.

mchusma 5y ago
Is it accurate to say the primary use of this is likely to design further quantum computers?
- krastanov 5y ago
  In a way, yes. I usually call such devices "technology demonstrators". But I am certain there would be researchers offended by such a trivialization of their work.
- haneefmubarak 5y ago
  Yeah the R&D that goes into this is mainly part of the longer term effort to make increasingly large quantum computers. In case you meant it the other way: the number of qubits here is still far too small for any real world application, including for simulations that would help design larger chips.
PeterisP 5y ago
What near term applications would be possible with just a 100 long-lived qubits?
- sz4kerto 5y ago
  For example routing algorithms used to change railroad traffic in case of a problem with a junction or track.
- krastanov 5y ago
  With long-lived ones, gosh, a ton. When you hear a researcher talk about "logical qubit" or less formally "long-lived qubit" they mean a reliable abstract computational component. When we talk about "physical qubits" we mean the unreliable real implementations like the one from this article. A rough rule of thumb is that you need a 1000 physical qubits to make one logical qubit. With 100 logical qubits (i.e. 100k physical qubits), you can start thinking about running chemistry simulations on the edge of what is possible with classical supercomputers. That is what I am excited about. There are also optimization problems, and some pretentious claims about quantum machine learning, which I am certain would be fun, but I am not as excited about. With 100 physical qubits, you can start testing non-trivial control schemes, circuit compilations, error correction methods, and many other building blocks.
tubby12345 5y ago
>a million "physical" qubits is a fairly reasonable guestimate. ... >If you are a quantum computation person developing near term applications, you probably would already start getting excited with a 100 (sufficiently long-lived) qubits. ... >"logical qubit" or less formally "long-lived qubit" ... With 100 logical qubits (i.e. 100k physical qubits) lol you're literally guilty of playing the same trick that people are bemoaning in another thread. incidentaly, having taken a QC systems class from Fred Chong, i believe you guys are all working on vaporware.
- krastanov 5y ago
  Read the second comment you are quoting to the end. I think you misread something.
  - tubby12345 5y ago
    This your lede answer to what is the smallest useful non toy QC: >If you are a quantum computation person developing near term applications, you probably would already start getting excited with a 100 (sufficiently long-lived) qubits. Then you go on and on and on and have one sentence about what you can do with 100 full stop period qubits. So what exactly did I misunderstand? It's just funny to me how all of you guys - from the crypto QC grifter, all the way to PIs and postdocs like you play the same word game
    - krastanov 5y ago
      I guess I should be more careful when using handwavy terms. "Long-lived" does not have a defined meaning, so in my second answer I spelled out what you can do with a bunch of "logical" qubits and with a bunch of "physical" qubits, providing clear definitions of these words. I am not sure why you are so angry about the use of a handwavy term though, given the whole point of this thread was to introduce the topic to lay people. Either way, the second comment is clear and it avoids the ill defined terms, so hopefully you would be happy with it if you read it in its full length. There is no such thing as "full stop period" qubits, hence the confusion.

mchusma 5y ago

Is it accurate to say the primary use of this is likely to design further quantum computers?

krastanov 5y ago
In a way, yes. I usually call such devices "technology demonstrators". But I am certain there would be researchers offended by such a trivialization of their work.
haneefmubarak 5y ago
Yeah the R&D that goes into this is mainly part of the longer term effort to make increasingly large quantum computers. In case you meant it the other way: the number of qubits here is still far too small for any real world application, including for simulations that would help design larger chips.

PeterisP 5y ago

What near term applications would be possible with just a 100 long-lived qubits?

sz4kerto 5y ago
For example routing algorithms used to change railroad traffic in case of a problem with a junction or track.
krastanov 5y ago
With long-lived ones, gosh, a ton. When you hear a researcher talk about "logical qubit" or less formally "long-lived qubit" they mean a reliable abstract computational component. When we talk about "physical qubits" we mean the unreliable real implementations like the one from this article. A rough rule of thumb is that you need a 1000 physical qubits to make one logical qubit. With 100 logical qubits (i.e. 100k physical qubits), you can start thinking about running chemistry simulations on the edge of what is possible with classical supercomputers. That is what I am excited about. There are also optimization problems, and some pretentious claims about quantum machine learning, which I am certain would be fun, but I am not as excited about. With 100 physical qubits, you can start testing non-trivial control schemes, circuit compilations, error correction methods, and many other building blocks.

tubby12345 5y ago

>a million "physical" qubits is a fairly reasonable guestimate. ... >If you are a quantum computation person developing near term applications, you probably would already start getting excited with a 100 (sufficiently long-lived) qubits. ... >"logical qubit" or less formally "long-lived qubit" ... With 100 logical qubits (i.e. 100k physical qubits) lol you're literally guilty of playing the same trick that people are bemoaning in another thread. incidentaly, having taken a QC systems class from Fred Chong, i believe you guys are all working on vaporware.

krastanov 5y ago
Read the second comment you are quoting to the end. I think you misread something.
- tubby12345 5y ago
  This your lede answer to what is the smallest useful non toy QC: >If you are a quantum computation person developing near term applications, you probably would already start getting excited with a 100 (sufficiently long-lived) qubits. Then you go on and on and on and have one sentence about what you can do with 100 full stop period qubits. So what exactly did I misunderstand? It's just funny to me how all of you guys - from the crypto QC grifter, all the way to PIs and postdocs like you play the same word game
  - krastanov 5y ago
    I guess I should be more careful when using handwavy terms. "Long-lived" does not have a defined meaning, so in my second answer I spelled out what you can do with a bunch of "logical" qubits and with a bunch of "physical" qubits, providing clear definitions of these words. I am not sure why you are so angry about the use of a handwavy term though, given the whole point of this thread was to introduce the topic to lay people. Either way, the second comment is clear and it avoids the ill defined terms, so hopefully you would be happy with it if you read it in its full length. There is no such thing as "full stop period" qubits, hence the confusion.