[HN Gopher] The quantum technology ecosystem explained
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The quantum technology ecosystem explained
Author : sblank
Score : 63 points
Date : 2022-03-22 17:34 UTC (1 days ago)
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| westurner wrote:
| Wikipedia (dbpedia, wikidata,) concept URIs:
|
| Category:Quantum mechanics
| https://en.wikipedia.org/wiki/Category:Quantum_mechanics
|
| Applications_of_quantum_mechanics
| https://en.wikipedia.org/wiki/Applications_of_quantum_mechan...
|
| List of emerging technologies
| https://en.wikipedia.org/wiki/List_of_emerging_technologies may
| have inspiration for applications of currently-discovered quantum
| mechanical phenomena.
|
| _#Q12_ is the Quantum K12 talent.
|
| QoS: Quantum-on-Silicon may very well scale; but how can we store
| un-collapsed output qubits?
|
| Quantum tagging,
| zardo wrote:
| > QoS: Quantum-on-Silicon may very well scale; but how can we
| store un-collapsed output qubits?
|
| Aren't all current programmable quantum processors essentially
| made of qubit memory cells capable of certain in-memory
| operations?
| NohatCoder wrote:
| All current programmable quantum processors are made from
| unicorn hairs and fairy dust.
|
| The current state of the art is trying to prove that the
| thing did _something_ quantum. Programmability is at best
| swapping some wires around to change that _something_.
| Strilanc wrote:
| Programming current quantum computers does not require
| swapping wires around. You can go to https://quantum-
| computing.ibm.com right now, drag some operations around in
| an editor, and have their quantum computer run those
| operations. No one is madly dashing around changing wires
| when you do that.
| westurner wrote:
| That was how they did it back in the old days though.
|
| Q: "Ask HN: What's the Equivalent of 'Hello, World' for a
| Quantum Computer?"
| https://news.ycombinator.com/item?id=22707580 [ IBM
| Qiskit, Microsoft Q#, Google TFQ TensorFlow Quantum,
| Google Cirq ([NumFOCUS,] SymPy) ]
|
| - https://www.tensorflow.org/quantum/tutorials/hello_many
| _worl...
|
| A: Set a register to zero and see how many times it reads
| as zero: A) in the local software simulator; and B) with
| just one _modern day_ qubit register.
| NohatCoder wrote:
| All the offered "quantum computers" are suspiciously
| easily simulated on a normal PC.
| reikonomusha wrote:
| 46 qubits of a perfectly ideal quantum computer require a
| petabyte of RAM to simulate, and about 10 quadrillion--if
| not more--arithmetic instructions to perform a single
| quantum instruction.
| klyrs wrote:
| Not if you try to simulate the _actual_ device under
| test, and not an idealized version of what it isn 't.
| Nothing suspicious about it, they're small and noisy.
| Scalability is extremely hard for quantum computers, and
| there's distinct tradeoffs that need to be made in their
| engineering.
|
| As far as I know, nobody in the industry is making absurd
| claims about their current offerings. That said, some
| claims of projected growth I've seen appear to be
| batshit.
|
| And, I believe that you're wrong: Google's quantum
| supremacy result appears to be genuine, and IBM's
| refutation was, essentially, "we can use a ginormous
| supercomputer to match that" -- not your ordinary
| desktop.
| reikonomusha wrote:
| This is false. Quantum computers are not programmed like
| telephone switch boards. They're programmed typically by
| sending signal pulses (of RF, DC, or light) of the right
| shape at the right time to physical elements and they
| react. It _really is_ programming.
|
| Moreover, it's remarkably easy to see that the machines--
| universal gate-based machines--are doing something quantum.
| What's not easy to see is if they'll ever break away from
| their scaling challenges and become useful, large scale
| machines.
| dekhn wrote:
| Well, NMR has been doing that for quite some time but
| nobody considers it "computing". Realistically, you're
| encoding a problem within a physical system by perturbing
| its energy levels, letting them evolve, and then doing
| readout. This works because computation is universal.
| reikonomusha wrote:
| Again, no. Maybe you're thinking about adiabatic quantum
| computation, something popularized by D-Wave. But most
| people in the industry don't call their machines
| "(universal) computers," but rather "quantum annealers."
|
| This is not the same as universal, gate-based
| computation, which does take an actual program containing
| instructions, and executes those instructions more-or-
| less sequentially, just as any computer programmer would
| expect. The state of the system begins with what is
| essentially equivalent to a large array of 0's, and you
| manipulate it accordingly, without resorting to evolution
| as your primary computational means of marching forward.
| In fact, left alone, these computers are designed to
| remain static, like an ordinary computer. (However, they
| still couple with the environment and decohere, which is
| one of the major challenges we, as humanity, face in
| building a _useful_ quantum computer.) This is what
| Rigetti, IBM, Google, HRL, Amazon, IonQ, ColdQuanta, etc.
| are doing. They use superconducting transmon qubits, ion
| qubits, neutral atom qubits, or silicon quantum dot
| qubits. (There are other companies and qubit technologies
| still.)
| dekhn wrote:
| Hey, um, I think I do know what I'm talking about :). You
| can see more of this historical side effort, which didn't
| pan out for a number of reasons: https://en.wikipedia.org
| /wiki/Nuclear_magnetic_resonance_qua... A 7 qubit QC NMR
| was implemented in 2001.
|
| All these systems are just evolution of spin systems or
| other similar systems. The big difference with an NMR
| quantum computer is that it manipulates ensembles of
| spins.
|
| The comment about universality of computing is that many
| physical processes can be used to compute things. I
| didn't say that qcs were universal computers.
|
| Please try to read what i'm writing more carefully.
| reikonomusha wrote:
| I know what NMR is. The systems are not evolutions of
| NMR. They're fundamentally different in their design,
| construction, and physics. An exchange-only silicon dot
| quantum computer is very different than an NMR quantum
| computer, which is very different than a neutral atom
| quantum computer.
|
| These computers, these days, are by and large considered
| _computers_ which _execute programs_. Perhaps in the
| 90s-00s that wasn 't the case since physicists cared more
| then about the construction of a laboratory apparatus and
| less about turning it into a programmable device with
| program and data I/O.
|
| I can't comment on what you know or don't know, but what
| you're writing is misleading and not accurate. The two
| points you've made (about what's considered computing and
| how modern quantum computers work) are what I refute.
| westurner wrote:
| "Quantum computing: A taxonomy, systematic review and
| future" (2022) https://doi.org/10.1002/spe.3039
|
| "Multi-qubit quantum logic operations with ion-implanted
| donor spins in silicon" (2022) https://scholar.google.com
| /citations?view_op=view_citation&h...
| https://meetings.aps.org/Meeting/MAR22/Session/G39.1
| (Veritasium video)
|
| > _Among semiconductor qubits, the electron and nuclear
| spins of donors in silicon play a special role for their
| conceptual simplicity (a 31P donor in silicon is similar
| to hydrogen in vacuum) and their exceptional coherence
| times [1] and 1-qubit gate fidelities [2]. Here I will
| present experimental progress on multi-qubit logic
| operations with donor spins, which point to several
| credible pathways for scalability using ion-implanted
| donors in MOS-compatible devices. The current state of
| the art is a hybrid electron-nuclear 3-qubit processor
| [3], where two 31P nuclear spin qubits are coupled to the
| same electron. The shared electron enables a geometric
| nuclear two-qubit CZ gate, which we perform with 99.37%
| average fidelity. NMR single-qubit gates reach fidelities
| up to 99.95%, and state preparation and measurement are
| performed with 98.95% fidelity. These three metrics show
| how close this system is to operating at fault-tolerance
| thresholds. Further, we entangle the two nuclei with the
| electron to prepare a 3-qubit GHZ state with 92.5%
| fidelity. Electron-nuclear entanglement unlocks the
| ability to connect nuclear qubits via the electrons, for
| instance using exchange interactions [4]. We have
| operated a weakly (~10 MHz) exchange-coupled 31P donor
| pair as a 2-qubit electron system, with native CROT gates
| performed by resonant microwaves. Gate fidelity
| benchmarks are underway and will be reported at the
| Meeting. On the engineering side, we have demonstrated
| the ability to implant single donors in silicon with
| confidence up to 99.85% [5]. This striking result
| identifies ion implantation as a scalable and accurate
| manufacturing strategy for spin-based quantum computers
| in silicon._
|
| QoS: Quantum-on-Silicon
|
| The survey article above just says "[Quantum] Output"? Is
| that different from registers? How long are those states
| ah coherent?
|
| "Researchers store a quantum bit for a record-breaking 20
| milliseconds" (2022)
| https://phys.org/news/2022-03-quantum-bit-fora-record-
| breaki...
|
| > _By managing to store a qubit in a crystal (a "memory")
| for 20 milliseconds, a team from the University of Geneva
| (UNIGE) has set a world record and taken a major step
| towards the development of long-distance quantum
| telecommunications networks._
|
| What are repeaters, and what are [quantum] prepared
| states in re: registers and longer-term storage for _non-
| collapsed_ (or just probabilistic?) qubit outputs?
| dekhn wrote:
| I don't understand your point. Everything I said above is
| completely and totally technically correct from a
| physical point of view. You are ascribing to my
| statements meaning which I did not intend.
|
| Modern trapped ion computers are doing the same
| underlying operations as NMR: you are using RF or other
| energy to perturb the energy states of underlying
| particles or other components, and reading out the
| results.
|
| There was also a whole field called 'dna computing' which
| you would call biologists in a lab, but they were
| absolutely doing computing
| reikonomusha wrote:
| I'm intently curious what sort of common-sense
| explanation you'd ascribe to how one programs an ordinary
| classical computer. Would you describe a computer
| programmer as one who orchestrates a delicate movement of
| charge through an intricate arrangement of n-p-n bipolar
| transistors?
|
| Quantum computers really can be instructed to do an
| abstract operation on an abstract quantity, just like I
| can on an ordinary computer. You tell quantum computers
| to add and multiply, just as you do in your favorite
| programming language. In the programming language Quil,
| which a couple quantum computers of different base
| technologies use, one can literally write down a matrix
| of numbers in a program to define a new mathematical
| function, and later use that function to manipulate the
| contents of the computer's RAM[1]. On top of this, you
| can have loops, boolean conditions, and all that jazz a
| programmer expects. You don't even need a physicist to do
| this; a completely physics-ignorant programmer could do
| this.
|
| All this business about energy levels, evolution, etc.
| are distractions, just as the electrodynamics of a
| transistor are distractions from what it means to program
| a computer.
|
| [1] I'm abusing the word "RAM" here, where I truly mean
| the state of your quantum register(s).
| westurner wrote:
| > _one can literally write down a matrix of numbers in a
| program to define a new mathematical function, and later
| use that function to manipulate the contents of the
| computer 's RAM[1]._
|
| This "Quantum Computing for Computer Scientists" video
| https://youtu.be/F_Riqjdh2oM explains classical and
| quantum operators as just matrices. What are other good
| references?
|
| Quantum state:
| https://en.wikipedia.org/wiki/Quantum_state
|
| Quantum logic; quantum logical operators:
| https://en.wikipedia.org/wiki/Quantum_logic
|
| > _All this business about energy levels, evolution, etc.
| are distractions, just as the electrodynamics of a
| transistor are distractions from what it means to program
| a computer._
|
| But a classical simulator - like e.g. qiskit - for a
| quantum circuit/experiment/function must run the
| experiment very^very^very many times to even
| probabilistically approximate a sufficient quantum
| system; because of the combinatorial probabilistic
| explosion that results from adding just one more basis
| state.
|
| What are the fundamental limitations of quantum
| simulators? Maybe it's possible.
|
| Quantum simulator:
| https://en.wikipedia.org/wiki/Quantum_simulator
|
| - [ ] Maybe Twistor theory has insight into a classical
| geometrical formulation that could be run on a non-QC?
|
| Amplituhedron:
| https://en.wikipedia.org/wiki/Amplituhedron
|
| [Photon] wave-particle constructive superpositions
| approximate which operators, which may form a neat
| topology like this:
|
| - [ ] > _A research question for a new school year:_
|
| > _The classical logical operators form a neat topology.
| Should we expect there to be such symmetry and structure
| amongst the quantum operators as well?_ https://commons.m
| .wikimedia.org/wiki/File:Logical_connective...
| reikonomusha wrote:
| Your assessment of how a quantum simulator works is not
| quite right. These simulators represent the entire
| probability distribution of basis states succinctly as an
| array. This array grows very large (exponentially) in the
| number of qubits.
|
| A simulator only needs to run a computation once (which
| is multiplication of matrices in a tensor product space)
| and look at the resulting state. You don't need to run
| anything multiple times to approximate a quantum state.
|
| The questions you're asking are the whole point of the
| field of quantum information science. On an ordinary
| quantum computer where quantum state will collapse to a
| basis state upon readout, indeed you might need to gather
| statistics to determine the answer to whatever you've
| asked your computer. However, "very many times" is
| mathematically bounded in some way for an ideal quantum
| computer. It's like saying "we need to do
| many^many^many^many comparisons to do quicksort". Well
| yes, but we have a relationship between the size of the
| input (N) and the average number of comparisons needed (N
| log N), which makes the algorithm feasible in practice.
| This is the same with quantum algorithms.
|
| There are also different kinds of quantum algorithms.
| Some are more probabilistic in nature. Others are--again
| in purely ideal circumstances--give you the right answer
| in one go.
|
| As a side note: It is very hard for me to read,
| understand, and respond to your comments. They seem like
| random buzzword soups and aren't very coherently put
| together, mixed with random links and references.
| westurner wrote:
| Re: error in simulators and actual QC hardware, which we
| do need for a reason: Quantum Error Correction #
| General_codes https://en.wikipedia.org/wiki/Quantum_error
| _correction#Gener...
|
| How to best quantize reals into matrices (~= tensors)? ht
| tps://en.wikipedia.org/wiki/Quantization_(signal_processi
| n...
|
| > _Peter Shor first discovered this method of formulating
| a quantum error correcting code by storing the
| information of one qubit onto a highly entangled state of
| nine qubits. A quantum error correcting code protects
| quantum information against errors of a limited form._
|
| Here's "Quantum Algorithm Zoo" by Microsoft Quantum:
| https://quantumalgorithmzoo.org/
|
| And "Timeline of quantum computing and communication" htt
| ps://en.wikipedia.org/wiki/Timeline_of_quantum_computing_
| ...
|
| I have a hard time with the idea that the outcome of the
| ultimate quantum simulation is a collapsed float.
|
| Quantum Monte Carlo:
| https://en.wikipedia.org/wiki/Quantum_Monte_Carlo :
|
| > _Quantum Monte Carlo encompasses a large family of
| computational methods whose common aim is the study of
| complex quantum systems. One of the major goals of these
| approaches is to provide a reliable solution (or an
| accurate approximation) of the quantum many-body
| problem._ [...] _The difficulty is however that solving
| the Schrodinger equation requires the knowledge of the
| many-body wave function in the many-body Hilbert space,
| which typically has an exponentially large size in the
| number of particles. Its solution for a reasonably large
| number of particles is therefore typically impossible,_
|
| What sorts of independent states can or should we map
| onto error-corrected qubits in an approximating system?
|
| Propagation of Uncertainty ... Numerical stability ...
| Chaotic convergence, ultimately, apparently:
| https://en.wikipedia.org/wiki/Propagation_of_uncertainty
| _sword wrote:
| All of the QC companies have "gone public" via SPAC mergers. Less
| oversight, more hockey stick revenue projections.
| ziofill wrote:
| not all of them
| latenightcoding wrote:
| all of them. IonQ, Rigetti, D-Wave.
| reikonomusha wrote:
| HRL Laboratories is very active in the field (if you happened
| to catch them at APS March Meeting) and hasn't been public
| since their founding in the 60s. It's one of the most respected
| private research laboratories of the United States. (It's
| currently jointly owned by Boeing and General Motors, but
| enjoys decision-making autonomy.)
| kvathupo wrote:
| Frankly, they had no other choice: public funding for quantum
| computing research is unacceptably low in the US. While China
| is funneling $10B into a single quantum lab [1], the US only
| spent $800M in the whole area for 2021 [2].
|
| I fear that we're repeating the same mistake we made with
| Machine Learning funding. A decade ago, the US was quite
| clearly ahead of China in machine learning, but they're
| comparable now. In quantum information science, the US is
| currently ahead of China in terms of research. But will it
| remain that way?
|
| For more information, here's a panel discussion on the quantum
| computing race between China and the US (I was quite frustrated
| by it):
|
| https://youtu.be/KzFEeQ49HHI
|
| [1] - https://english.ckgsb.edu.cn/knowledges/quantum-wars/
|
| [2] - https://quantumcomputingreport.com/u-s-qis-budget-
| proposed-t...
| bashmelek wrote:
| For anyone interested, IBM quantum experience lets you simulate
| quantum computer operation, and even gives an allowance of
| running actual simple programs, made in their visual tool
| "composer", on a real quantum device, through the api. Signup
| required for some things. https://quantum-
| computing.ibm.com/composer/files/new
| mikewave wrote:
| You can also sign up for D-Wave Leap and use our online IDE,
| problem visualizer, and submit problems to our QPUs with a free
| signup. https://cloud.dwavesys.com/leap/
| NohatCoder wrote:
| The article mention that NSA have objected to quantum key
| distribution, then go on to state: _However, if you're a
| commercial company these systems may be worth exploring._ The
| problem that NSA and many others have pointed out is that it
| doesn 't solve any actual problems. It creates a bunch of hassles
| but can't replace asymmetric cryptography.
| grobclaw wrote:
| Correctly implemented QKD gives you key distribution without
| assumptions about how difficult certain mathematical problems
| are in relation to how much compute your adversary has. Key
| distribution is nowadays done with assymetric cryptography, so
| QKD can replace some assymmetric cryptography. You can also
| have authentication (Wegman-Carter) with symmetric keys. What's
| not quite clear is how you would do certificates and PKI.
| However, given key distribution, you could probably use
| symmetric keys for that as well.
|
| It's unlikely that your adversaries can decrypt your traffic
| right now (break things like RSA). However, advances in number
| theory and/or computing power might enable them to do that in
| the future. Your adversary can just record your encrypted
| traffic and wait until the means to decrypt it become
| available. Thus, for data that has to stay secure for a long
| time (and where you want to be as sure as possible that it
| will) it's not good to rely on predictions into the future
| about advances in number theory or computing. This is the niche
| that QKD is aiming at.
|
| For what it's worth, China has a huge QKD network, which cost
| them a lot of money. Their QKD satellite also cost a lot of
| money. They are in fact world leaders in quantum communication
| technology as well and spend a lot on researching it. I wonder
| why they made this investment, whether it was smart, and what
| they get out of it.
|
| I also have doubts that QKD will see much use in the coming
| decades and even more doubts that its use will be done properly
| and actually make a lot of systems more secure. Securing
| systems is very hard and securing individual communication
| links (what QKD does) is not the main problem. In the current
| landscape, securing your data and communications to a
| reasonable level just isn't worth it for the vast majority of
| buisnesses, since they can offload most of the damages of being
| breached to their customers. There is a danger that QKD will be
| seen as "magic fairy dust" that you sprinkle over your systems
| just to claim you're trying very hard to secure them (this
| image is still widespread about standard cryptography as well).
| beloch wrote:
| To put it briefly,
|
| Messages sent using classical crypto should be viewed as
| being public after an unknown delay. They can be decoded at
| your adversary's leisure with techniques and equipment
| invented in the future.
|
| Quantum cyrpto must be broken _immediately_ to be broken at
| all.
|
| If what you are encrypting is, for example, credit card
| information, it's perfectly fine if that becomes public in a
| decade. Your information will have changed.
|
| If what you are encrypting needs to remain secret for the
| next fifty years, do _not_ use classical encyrption and a
| public channel. It may well be made public while the
| information is still sensitive. This is why QKD has some
| early adopters. It 's the only long-term secure alternative
| to having people carry one time pad's back and forth in
| suitcases full of hard drives, which has its own security
| issues.
| amelius wrote:
| > If what you are encrypting needs to remain secret for the
| next fifty years
|
| Just add one bit and make it 100 years. By that time,
| nobody will care really.
| kaicode2 wrote:
| Quantum imaging was an application I was not aware of until
| reading this. Tremendously exciting. Great post.
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