Hasn’t been much that I’ve heard about worth discussing here recently. Presumably everyone is on vacation. I’ll try and gather some things that may be of interest, starting first with the hot topic of “quantum computation”. It looks like this will be drawing an increasing amount of attention and resources in the field of physics research. For instance:

- Slides and videos from the summer IAS program From Qubits to Spacetime are available here.
- There will be a graduate seminar at Harvard this fall, blog post about it here.
- In a few weeks Fermilab will host a workshop on Next steps in Quantum Science for HEP.
- Moving through the US Congress is a National Quantum Initiative Act, which would provide over a billion dollars in funding for things related to quantum computation.
- At the NSF MPS (Mathematics and Physical Sciences) they’re promoting NSF’s Quantum Leap. This is the first of four “Big Ideas” (discussed here) which will influence what gets funded. The other three are multi-messenger astrophysics, big data, and things related to biology.
- Launching this week is The NSF 2026 Idea Machine, which is a competition for suggesting research questions, more “Big Ideas” for the NSF to fund. If you want to enter the competition that opens Friday, I’m guessing that invoking the word “Quantum” will help.

Also, Scott Aaronson has a new set of notes on quantum information:

https://www.scottaaronson.com/blog/?p=3943

Interesting that Witten seems to have switched fields into quantum computing.

Thank you for the nice series of links. I’m a hardware guy and found this one useful (from the NSF Big Ideas.)

https://www.nsf.gov/attachments/245240/public/materials_for_quantum_leap.pdf

Is it just me, or does this seem like a lot of hype? (Topological insulators as the next transistor?)

Maybe I am naive, but can someone tell me how quantum computing provide insights on Physics beyond standard model (or just more insights into standard model) or give clues on what LHC would see?

Shantanu,

I don’t think any of this has any relations to questions about the SM or possible BSM physics. In some sense, the move to this study of new quantum materials and quantum computation marks a giving up on the idea of trying to understand more about the SM.

There seems to be some hope that this will lead to new ideas about quantum gravity and, especially, how to resolve the black hole information paradox. I haven’t had time to look into this carefully, but from what I’ve seen, the ideas about quantum gravity seem extremely crude, untestable, and explain nothing at all about the relation of quantum gravity to the SM.

Peter,

Wouldn’t quantum computation allow us to simulate the SM and BSM physics to perhaps get new insights into these models of physics?

Stephen Marney,

The problem is that most of the mysteries of the SM have to do with what appear to be weakly coupled degrees of freedom, where perturbation theory is a very effective computational tool and I don’t see how quantum computers would help. The strongly interacting sector of the theory is one where maybe quantum computers will help, but all evidence is that there the dynamics is known and fixed (SU(3) Yang-Mills).

For a different perspective, I see that Sabine Hossenfelder has a new piece out in Quanta:

https://www.quantamagazine.org/the-end-of-theoretical-physics-as-we-know-it-20180827/

The main reference to the SM there is

“maybe what we currently think of as fundamental — space and time and the 25 particles that make up the Standard Model of particle physics — is made up of an underlying structure, too. ”

but my problem with this sort of claim is that I’ve never seen a plausible idea for what this new “underlying structure” is supposed to be.

There is an important aspect of testing SM and BSM physics, and that in many cases, for example in dark matter detection, neutrinoless double-beta decay, and neutrino cross sections, and that’s one needs the interaction matrix element between particles and nuclei; and to get accurate results one needs to solve the nuclear many-body problem well. I know, I know, you all probably think this is either “long ago solved physics” or “black box physics,” but neither is true. (It happens to be my area of research.) The last 15 years have seen tremendous improvement in rigorous calculations of the nuclear many-body problem…but mostly for light nuclei (lighter than oxygen), and many of the interesting targets are heavy (like xenon). So the idea here is to do nuclear many -body calculations on heavy nuclei with quantum computers.

Now, will quantum computers actually be able to outperform classical computers in this regard? And if so, how soon? Well, that’s the question.

(And, no, density function theory isn’t enough for some of these calculations. And coupled clusters only work well near closed shells.)

A google search for “quantum computing” gave me as first hit a

report by Accenture https://www.accenture.com/t20170628T011725Z__w__/us-en/_acnmedia/PDF-54/Accenture-807510-Quantum-Computing-RGB-V02.pdf#zoom=50 which mentions, as the first possible application in Table 1

“portfolio selection”, which I guess means stock picking. Oh boy.

CWJ,

Simulating complex quantum systems is precisely what quantum computers will be good for. Shor’s algorithm gets a lot of attention, for obvious reasons, but there is no fundamental reason why quantum computers should be good at factoring, or why classical computers should be bad at it.

On the other hand, the idea that any physical system at all can be efficiently simulated by a digital quantum computer is taken seriously by a lot of the community (it is known as the Church-Turing-Deutsch thesis), and I personally would be shocked if a xenon nucleus turned out to be intractable.

Mateus,

I agree that quantum computers *ought* to be good for modeling complex quantum systems. But in practice it may be very different.

Fortunately, a paper on the arXiv just appeared, explaining how to do this for quantum many body systems (atoms, but presumably I can translate it to nuclei). Now I just need to find the time to read it….

https://arxiv.org/abs/1808.10402