Scientists Just Measured a Mechanical Quantum System Without Destroying It:
There's a key aspect of quantum computing you may not have thought about before. Called 'quantum non-demolition measurements', they refer to observing certain quantum states without destroying them in the process.
If we want to put together a functioning quantum computer, not having it break down every second while calculations are made would obviously be helpful. Now, scientists have described a new technique for recording quantum non-demolition measurements that shows a lot of promise.
In this case, the research involved mechanical quantum systems – objects that are relatively large in quantum computing terms, but exceedingly tiny for us. They use mechanical motion (such as vibration) to handle the necessary quantum magic, and they can be combined with other quantum systems too.
[...] They describe it as similar to playing a theremin, the strange musical instrument that doesn't need to be touched to produce sound.
[...] A hybrid qubit-resonator device such as the one described in this study potentially offers the best of two different fields of research: the computational capabilities of superconducting qubits, and the stability of mechanical systems. Now scientists have shown information can be extracted from such a device in a non-destructive way.
Plenty more work needs to be done – once the task of measuring states has been refined and completed, these states then need to be exploited and manipulated to be of real use – but the huge potential of quantum computing systems may have just been brought another step closer.
The article also includes a video of someone playing a theremin.
Journal Reference:
von Lüpke, U., Yang, Y., Bild, M. et al. Parity measurement in the strong dispersive regime of circuit quantum acoustodynamics. Nat. Phys. (2022).
DOI: 10.1038/s41567-022-01591-2
(Score: 3, Funny) by calmond on Wednesday May 25 2022, @12:55PM (2 children)
Well, was it alive or not?!?!
(Score: 0) by Anonymous Coward on Wednesday May 25 2022, @02:22PM (1 child)
Since they didn't disturb it, they couldn't tell if it was dead or just sleeping.
(Score: 0) by Anonymous Coward on Wednesday May 25 2022, @03:36PM
the experimenter did not live to tell the tale...
i find it funny that the case, where "magic" happens get dismissed right out of hand when it comes to quantum conform solutions.
heaven and hell get moved to "fix" and "solve" the "look and disturb" problem but who is to say that a tiny point questioned so hard will not agree by changing everything else around it?
so the WORKING quantum computer might not even be a computer at all but a device to change reality around itself?
(Score: 3, Interesting) by inertnet on Wednesday May 25 2022, @01:59PM (2 children)
Here's a video [youtube.com] of someone playing a theremin in a more modern way.
(Score: 0) by Anonymous Coward on Wednesday May 25 2022, @02:25PM (1 child)
That was really cool.
(Score: 2) by inertnet on Wednesday May 25 2022, @10:16PM
I know, that guy is some kind of genius.
(Score: 2) by JoeMerchant on Wednesday May 25 2022, @02:28PM (5 children)
Does this apply to all quantum states, or are some "guaranteed" to be demolished on reading?
Україна досі не є частиною Росії Слава Україні🌻 https://news.stanford.edu/2023/02/17/will-russia-ukraine-war-end
(Score: 3, Informative) by maxwell demon on Wednesday May 25 2022, @02:51PM (4 children)
From Wikipedia: [wikipedia.org]
The Tao of math: The numbers you can count are not the real numbers.
(Score: 3, Interesting) by JoeMerchant on Wednesday May 25 2022, @04:17PM (3 children)
But... can a single photon be "read" by a man-in-the middle, collapsing the wave function, but still undetectable by the receiver on the end of the intended comm channel?
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.89.187901 [aps.org]
Україна досі не є частиною Росії Слава Україні🌻 https://news.stanford.edu/2023/02/17/will-russia-ukraine-war-end
(Score: 2) by maxwell demon on Wednesday May 25 2022, @08:38PM (2 children)
No. All quantum key protocols are designed with the assumption that the attacker can do a non-demolition measurement.
The Tao of math: The numbers you can count are not the real numbers.
(Score: 2) by JoeMerchant on Wednesday May 25 2022, @08:56PM (1 child)
Then how is the attacker prevented from receiving the exact same information as the intended recipient?
Україна досі не є частиною Росії Слава Україні🌻 https://news.stanford.edu/2023/02/17/will-russia-ukraine-war-end
(Score: 5, Informative) by maxwell demon on Thursday May 26 2022, @05:04AM
All QKD protocols involve measurements in randomly chosen non-commuting bases. Here non-commuting means that measuring one will change the results of measuring the other afterwards (by the collapse of the wave function, so this is true even for non-demolition measurements).
Indeed, it goes even further: The attacker might try to avoid the collapse of the wave function by doing some quantum interaction with a system in his control, and only do the measurement after the communicating parties finished the protocol. However even that dies not help: The no-cloning theorem shows that the attacker can't simply make a copy of the quantum state (if he could, he indeed could just replicate the relevant measurements based on the communication on the public channel after the communicating parties made their measurements (they do have to exchange the information in order to arrvie at a common key, and the base assumption on QKD protocols is that the attacker can listen on any classical communication channel). So to gain any information afterwards, the attacker would have to entangle his quantum system with the transmitted quantum state. But that already changes the outcome statistics in the very same way as if a measurement had been performed (in other words, it's not really the measurement that changes the statistics, but the very fact that the system has been interacted with in a way that now another system can be used to gain information about it).
Now QKD protocols either involve the communicating parties to explicitly check the statistics and throw away the generated key if interference was detected (thus the attacker does have information about the key, but it doesn't help him as the the communicating parties know that and won't use it. Or the QKD is designed in a way that the communicating parties won't get a common key that way at all; in this case there is nothing for the attacker to know.
The Tao of math: The numbers you can count are not the real numbers.
(Score: 2, Interesting) by Anonymous Coward on Wednesday May 25 2022, @05:24PM
Principle of Least Action as with Feynman Path Integral adds up all the possible conditions in the quantum state, so we do not have a future dependency problem.
In reality though, only 1 state exists required for the measurement postulate.
We can jump up and down when they actually make the computer and show us proof.
Cause this just sounds too good to be possible.
Imagine we get to have our 90s Internet back!
Everything is running faster cause we can offload all the crypto in our protocols. /dream
IF they get a computer to actually use this as intended, it may just very well be the start of a "technological singularity".
Then this news will be a real game changer.
(Score: 2, Funny) by Anonymous Coward on Wednesday May 25 2022, @06:47PM
It's what makes transporters work.