Author: dabacon

In my last post I described a list created by the late physicist John Archibald Wheeler describing ways in which the universe could be like a computer. This came from a note in the collection of papers from the American Philosophical Society. In the second part of this note, Wheeler moved on to describing what the possible implications of the metaphor could be. I’ve now transcribed these and thought people would be interested in seeing this list as well.

THE UNIVERSE AS A COMPUTER

Possible Implications of the Metaphor

NOTE: The prior and companion list ”The Universe As A Computer: Possible Meanings of the Metaphor”–which should also be consulted–dealt with the metaphor in a more preliminary, general, and abstract way. Here there is an effort to list the more specific, concrete mechanisms that may permit important analogies between computers and universes-~apart from items that would be largely redundant if added to this second list (apart, in turn, from oversights that are inevitable in this unedited list, and items whose redundancy is initially uncertain). Some items here are apt to represent particular illustrative or applied examples, or sets thereof, rather than unique conceptual taxons restricted to, and precised and exhausted by, single items.

1. Physical phenomena and entities may have spontaneous or reactive output effects that occasionally, often, generally, or always elicit or modify one or more instances, modes, or kinds (contents) of direct or indirect feedbacks from near, distant, and/or all (pancosmic) entities, phenomena, events, or environments–of a like or different nature–in one or more or infinitely many cycles, phases, epochs, or progressions.

2. The former (see #1) may or may not be essential to the nature of the original physical phenomena and entities; that which is essential to the latter may be fixed substance or pattern, dynamic substance or pattern, dynamic interaction, dynamic transaction, ever-changing ever-novel modes thereof, or all such things combined.

3. Such feedback (see ## 1, 2) may be stabilizing and/or differentiating.

4. Such feedback (see ## 1, 2, 3) may be to the physical phenomena and entities, other feedback(s), and/or itself en route.

5. Such feedback (see ## 1, 2, 3, 4) may be (in addition to #3)–or have roles or elements that include–positive and negative feedback, alternation, correction, redirection, coupling, transportation, partitioning, rate control, memory, simplification, integration, comparing, measurement, intermediation and message-passing, path-finding, road maintenance, consolidation, sampling, &c.

6. Some or all parts of the physical universe may govern one another in a rotating system, that is fixed and/or random in various ways and degrees.

7. In some way the universe may resemble a representative democracy, with fixed or changing particular or general representatives, arranged in a finite or infinite hierarchy, with government descending and/or ascending in various degrees, ways, and with respect to various matters.

8. The feedback proposed above (see ## 1-5) may form various finite or  infinite–and essential or nonessential–hierarchies, networks, series, channels, matrices, equilibria, disequilibria, phenomena,  systems, logics, ‘machines’, dimensions, clusters in maps, ‘stories’, lattices, equations, number systems, mathematical groups, categories, or analogs thereto, codes, &c.

9. Nature may everywhere be using simple arithmetic~-or other extraordinarily simple or universal processes–or may be characterizable by such to a wholly unexpected degree.

10. All of history may somehow represent a memory that is intact and functioning in the present.

11. Analogously (see #10), all of the future may somehow represent a plan  that is exhaustively immanent and active in the present.

12. All that a physicist is or does may somehow be–truthfully or pragmatically–reduced to a computer or computation.

13. The difference between the analogue and digital computer may not be sharp but rather represent a continuous gradation or a definitional or ultimate fiction.

14. The universe may approximate to a computer.

15. In an ultimate sense the universe may not be a computer, but the form of physics we have now, or that will emerge in the immediate future, may in essence treat it as such.

16. Representing the universe as computer-like, in physics and other natural sciences or science in general, might be a more–or the most–efficient, fertile, clever, unified, powerful, rational, or practical way of investigating, understanding, and exploiting it.

17. Much that we think of as essential and important in the present language, form, methods, philosophy, conceptual apparatus, mathematics, and overall organization of physics–even its ideals or standards of proof, rigor, consistency, elegance, simplicity, uniquity, universality, fundamentality, necessity, repetition, conceptuality, meaning, importance, finality, objectivity, completeness, predictive power, Boolean logic, &c–may not be, or may not be essential or important to physics as it could be, or as it should and will be in the future (perhaps thanks to the computer, as that which aids or supersedes the human scientist); that which is really essential and important in or to physics may be very different than we now suppose.

18. What goes on in and constitutes Nature may be much more steplike than we now know or suppose: the density, intricacy, and breadth of steps may be far greater, the steps may be far more discrete, individualized, important, coordinated, lawful, and elegant, phenomena and Nature as a whole may be much more concatenated, sequential, plexiform, stringy or I-dimensional, anastomotic, self-entraining, modular and nodal, unidirectional, irreversible, delomorphous, Functional, irredundant, operational, machinelike, constrained, local, tiny or microphysical, quantized, systemic, produced by massive past experimentation, selection, and evolution, organismic, organic, &c, the ‘wheel of time may have far more teeth’, Nature may be far more ruled, methodic, and nomocratic, &c.

19. The universe may everywhere be filled with local operations or activities that never cease and that are all simultaneously important~-perhaps locally, perhaps universally. 

20. Modern statistical cosmology may be a necessary early approximation that will ultimately yield to a complete cosmology wherefor the universe is essentially and irreducibly an infinitely complex machine that, qua infinitely complex, transcends the very concept of machine and of a mechanistic universe. 

21. The presumption of current physics that its laws, theories, methods, and concepts actually specify, describe, explain, or are equivalent –in any final, realistic, or sufficient way–to the detailed, peculiar, and total phenomena that fill all size scales in Nature as a single, indivisible, necessary, and solid plenum, may be a fantastic oversimplification. The truth may more nearly be that each and every phenomenon and event must speak for itself–that today’s physics offers only the crudest approximation to anything.

22. All physical phenomena locally, and the universe as a whole, may basically represent a process of counting.

23. What all interactions of physical phenomena may basically represent is a process of mutual description.

24. The universe may reduce to games being played between physical phenomena–games computable by or similar to a computer.

25. The role of the genes and genome in the reproduction, ontogeny, maintenance, life, and evolution of organisms–the control by the genotype of the phenotype–is essentially computer-like: and it may be that all physical phenomena, and the universe as a whole, are somehow controlled by analogous means and therefore also computer-like or computational. (In many instances or in general, the controlling system may be purely dynamical and hence for all purposes invisible, immaterial, and transcendental!)

26. The totality of physical phenomena constituting the universe may all–everywhere and incessantly–be evolutionary and coevolutionary.

27. All physical phenomena (in partial analogy to #25)–pace modern physics–may be largely or exquisitely controlled by a single, relatively or infinitely small, singularity-like internal locus, part, structure, dynamical program, law, process, idea, and/or the like exercising autocratic or mentorial powers.

28. Nature, by analogy with what goes on in a computer, may contain what could be described as ‘blocks of information, controls, or programs  that enable phenomena to control other phenomena, or at least to alter their function or influence the world as a whole, that may move about between phenomena and live a semi-independent existence, and that man could use as tools to decipher, control, and transform particular phenomena and phenomena in general.

29. The universe may represent information, forms of information, descriptions of itself, representations, or perspectives that are all competing with one another to emerge or dominate.

30. All parts of the universe may be competing to become the whole or to absorb one another.

31. The universe may represent a grid, tape, manifold, circuit, and/or the like that is curved, finite, closed, recursive, self-generating, self-exciting, teleological, circumplexed, and/or the like with respect to space, time, energy, matter, causes, effects, information, laws, and/or the like.

32. The universe may represent patterns of change or dynamical patterns, exponential processes, equations, types of order, states, morphogenetic tendencies, and/or the like that are all simultaneously competing to annihilate one another, originate, become maximally real or ‘probable’, become omnipotent or infinite, become ubiquitous or eternal, pullulate, interfere with one another, and/or the like.

33. Like a computer, the universe may contain null or zero elements that are active and important.

34. The universe may be creating time by gradually computing the future.

35. The universe may be like a computer operating on the fabric of the present to modify it and thereby create or synthesize the future.

36. The universe may be completely stoichiometric–perfectly conserving information, change, order, motion, states, possibilities, and/or the like.

37. The universe may be ‘nomogenetic’–constantly generating, discovering, and acquiring by transformation new, novel, more powerful, and more numerous laws and rules.

38. Per contra what the laws of thermodynamics seem to imply, usable energy and net order in the universe may be perfectly conserved rather than inevitably tending to decrease with time, and the universe may be equivalent to perpetual motion.

39. The universe may contain an indefinite amount of things that are hidden, just as a computer may hide its contents.

40. The universe may represent a computer whose program is unknowingly being  written, or rewritten, by the physicists themselves or by human minds in general.

41. Mastery of the flow and possibilities of physical information on the quantum scale, or in matter at all scales simultaneously, may equip man with the highest possible form of technology or mean that he has at last triumphed over Nature; and the secret to such mastery may be to treat the universe–scientifically or technologically–as a computer.

42. It may be possible to invent, make, and exploit cellular automata that are cosmoplastic and cosmopoietic (that can automatically change the entire universe or create new universes), the natural preexistence of such automata may be unavoidable (in which case Nature herself may be entirely artificial, and physics must reinvestigate the universe from the new point of view), and/or the power of such automata to effectively transform the content of the universe by simply redefining its form or by sampling it in a certain way to an infinite degree may mean that the universe is equivalent to a myriorama (a thing that gives the appearance of being a single universe, but in fact contains all possible universes and permits their efficient substitution).

43. The main lesson from the computer for today’s physicist may be that the universe is not just a thing that sits out there–simple, objective, absolute, independent of the observer, static, the manifestation of a few universal laws–but a complex construction, and a kaleidoscope composed entirely of active processes and interactive possibilities that call for a new physics telling the physicist how to do things and how to co-operate with, and as, the universe in a new and higher form.

THE UNIVERSE AS A COMPUTER

What I love about this and also about the previous list is that it is a mixture of the mundane and slightly insane. When I think of Wheeler I often think of this contradiction, in that he was very conservative in many respects, but also completely open to very odd ideas (there is only one electron in the universe !) Or to quote his student Richard Feynman, “Some people think Wheeler’s gotten crazy in his later years; but he’s always been crazy.”

In this list the one that jumps out as me is “Mastery of the flow and possibilities of physical information on the quantum scale, or in matter at all scales simultaneously, may equip man with the highest possible form of technology or mean that he has at last triumphed over Nature; and the secret to such mastery may be to treat the universe–scientifically or technologically–as a computer.” I think in this quote, from 1980, we’ve now tracked down the origin of all of the quantum computing hype!

Another one that I find great to see is 39, “The universe may contain an indefinite amount of things that are hidden, just as a computer may hide its contents.” In many ways, this is is the content of the Kochen-Specker-Bell theorem which shows that quantum theory is contextual.

Also 7, where he suggests the universe may be a representative democracy, isn’t something I expected, but I’m hoping Ted Chiang sees this blog post and decides to write a story about this idea.

I’m also thinking I’m not the only one who had to look up the pullulate (“multiply or spread prolifically or rapidly”).

John Archibald Wheeler is a bit of a hero for me (and also, like all good heroes a bit of a villain). Discovering his paper “It from Bit” was definitely a huge inspiration for me to get into the field. When I found Wheeler’s paper it led me to Bill Wootters work, and I immediately charged my parents hundreds of dollars to get a copy of very paper Bill had written (I mean who wouldn’t want to read “Quantum mechanics without probability amplitudes“) Amusingly these days I think many who claim the mantle of “it from bit” have not actually read the paper, which is quite radical, you should definitely stop reading this blog and read the paper if you have not.

Because Wheeler is someone who I’ve always been interested in, I was Googling (company plug) around the other day and found out the the American Philosophical Society has a collection with papers, notes, etc from Wheeler. Among these is a typed up note that I don’t think ever made it into a paper, but which I really loved. The title of the note is “THE UNIVERSE AS A COMPUTER”, and is dated “[1980?]”. In it Wheeler first lists possible meanings for the expression “the universe as a computer” followed by possible implications for this metaphor. And by list, I don’t mean a small list, he puts down 48 possible meanings. I love it.

Here are Wheeler’s possible meanings for the metaphor:

THE UNIVERSE AS A COMPUTER |  [1980?]

Possible Meanings of the Metaphor

NOTE: Such metaphors tend to be at once useful and misleading. They are understood only intuitively, vaguely, partially, ambiguously, and abstractly by their authors and users. They are apt to be polysemous–possessed of  multiple and complex meanings, both relevant and irrelevant. Moreover, in the present instance the utilitarian and natural meaning of the very words universe and computer is unknown to an indefinite degree! Physicists who are trying to conceive a new cosmology based in part on the metaphor of the universe as a computer may find the following list clarifying, heuristic, provocative, useful for self-criticism or discussion, &c. It is a partial list that needs to be extended, systematized, edited, explained, and illuminated by examples and corollaries.

1. May be more or less similar or identical to a Turing machine or serial computer, or be wholly or partly I-dimensional.

2. May comprise the equivalent of serial computers operating, either independently or interdependently, in a parallel array.

3. May resemble more nearly a completely parallel computer whose elements are not sub-computers.

4. May represent a hybrid serial and parallel computer.

5. May represent a hierarchy, network, and/or series of many serial or parallel computers.

6. May represent an infinite or finite set of computers.

7. May represent a computer of infinite size, complexity, subdivisibilit (componentry), age, lifespan, sophistication, perfection, power, connectivity, programming, knowledge, intelligence, dimensionality, activity, strangeness, and/or the like.

8. May (or physics may) reduce to pure mathematics, numbers, or ‘order’.

9. May use or reduce entirely to information, symbols, computer-like rules, states, decisions, operations, markers, pointers, arrays, structures, programs, sets, and/or the like.

10. May be like a computer in being instructible and programmable–or re-instructible, re-programmable, controllable, and manipulable. |

11. May reduce to a computer at a higher, lower, or ultimate level (scale).

12. May be treated as equivalent to a computer if the treatment is sufficiently elaborate, universal, clever, and/or absolute.

13. May represent a set of (finitely or infinitely) homogeneous or heterogeneous computers.

14. May represent a digital or binary computer.

15. May represent an analogue computer of finite, infinite, or infinitesimal self-similarity.

16. May be mechanical in the sense of being possessed of machinelike entities or phenomena–or of parts, operations, laws, &c that are surprisingly or absolutely simple, regular, interchangeable,  interlocking, perfect, universal, reliable, deterministic, knowable, predictable, finite, utilitarian, teleological, rational, constructible, symmetric, efficient, irreducible, repetitive, and/or the like.

17. May behave like a computer on occasion or in special situations.

18. May use a (central or omnipresent) model of itself.

19. May be simulated by a computer with arbitrarily great accuracy.

20. May represent a superficial pattern projected, in effect, on a background–or something like a program or simulation of a universe that is running on an independent and truly real computer but 1s not itself real or fundamental.

21. All natural phenomena, entities, and systems (be they trees, rocks, : molecules, bacteria, men, societies, rivers, stars, diseases, clouds, or whatever) may be computers or computer-like (have  programs, perform computations, use circuitry, possess memory, use languages, process information, use Boolean logic, or the like).

22. May be clock-like or use universally or locally synchronized parts or processes. 

23. All known laws may be controlled or created by higher laws (possibly  arranged in a hierarchy or network). :

24. The universe or all physical phenomena may be reducible to computation or a single great calculation.

25. May reduce to or be controlled by, or be expressible as, pure (Boolean or non-Boolean) logic.

26. May be a mind, mind-like, or thought-like, or be reducible to or treatable by pure thought.

27. May possess a (finite or infinite) computer-like or other memory; or memories and memory processes may exist in all natural phenomena (trees, rocks, genomes, &c).

28. May wholly or in part consist of cellular automata, or be a single great or infinite cellular automaton.

29. Physical processes, phenomena, entities, events, quantities, laws, states, and relationships (such as apparent movement, mass, fundamental physical constants, particle populations, 3-space, spacetime, volcanoes, and ocean waves) may be representational, programmatic, or computational illustons~~-or be infinitely ambiguous–rather than truly fundamental or real; and per se, may be alterable or transcendable by gaining knowledge of and control over their ‘programs’ or an equivalent. Put otherwise, all phenomena, &C may appear or behave as they do because of internal programs, self-models, rules, or computation to which man can gain access.

30. May be a lattice–or spacetime may be wholly quantized.

31. All quantum numbers may reduce to a single quantum number.

32. May essentially represent but a single, individual particle, event, or computer (that somehow generates the illusion of a multifarious world); or a single iterative or recursive operation repeating itself forever or toward a finite future destiny.

33. May represent more or less homogeneous or heterogeneous iterative or recursive processes, entities, phenomena, laws, quanta, measurements, disturbances, &c.

34. It may be possible to show that information and computation are fundamentally indistinguishable and hence equivalent, or that all of the following must in a similar way be equivalent: information, computation, energy, mass, space, time, and/or the like.

35. May be an asynchronous computer (computer with asynchronous parts).

36. May be a computer that functions statistically and indeterministically.

37. May be more or less lifelike (possessed of biological features such as homeostasis, growth, self-reproduction, self-evolution, competition, purpose, or memory).

38. As science progresses and becomes more complex, difficult, mathematical, and abstract, reliance on the computer may become total; and this may make a purely computational representation of the universe expedient, and justify present-day steps in that direction.

39. No one knows how simple, powerful, universal, natural, and/or complex computers might ultimately become–and it might be in these  ultimate senses that the universe is or resembles a ‘computer’.  (It might even be possible to devise revolutionary types of computers by studying and applying computational or computer-like properties of the universe.)

40. May function in ways similar or identical to such computer or mental  processes as generalization, recognition, categorization, error  correction, time sequence retention, induction, symbolic logic, analogical reasoning, and/or the like.

41. May use holonomical memory, correlations, or laws, something like a computer’s content-addressable memory, and/or the like. |

42. May represent an anastomotic network of everywhere diverging, converging,and interacting causes and effects, and in this way resemble a computer’s structure and functioning.

43. May be in some profound sense a function of the mind, and hence half-mental; or respond in entirely different ways dependent on how it is ‘addressed’.

44. Local phenomena may be controlled from a distance or by larger systems.

45. May represent a great hierarchical network of specialized ‘administrators’ or ‘administrative! processes, functions, systems, laws, constraints, &c. Also, may contain things analogous to questions, answers, experiments, orders, requests, negotiations, conversations, messages, traffic cops, supervisors, inspectors, translators, arbitrators, pioneers, &c.

46. May be totally finitistic–or finite everywhere and in every way.

47. May be ‘centralized’ and ‘centralistically’ controlled.

48. All that exists in the universe (including relationships, entities, interactions, laws, &c that are conventionally thought of as being inert, static, or time-invariant) may in fact be time-asymmetric or an uninterrupted process of change or of cosmoplastic or cosmopoietic interadjustments and interchanges; in this ‘everywhere~ always~novel universe! work and information-processing could be omnipresent and quintessential.

–THE UNIVERSE AS A COMPUTER

There are a couple of things that struck me in this list. The first is number 39. “39. No one knows how simple, powerful, universal, natural, and/or complex computers might ultimately become–and it might be in these  ultimate senses that the universe is or resembles a ‘computer’.  (It might even be possible to devise revolutionary types of computers by studying and applying computational or computer-like properties of the universe.) ” If this is truly 1980, this is pretty amazing because it is at its heart a statement that the universe’s computation may be very powerful, and that this might lead us to more powerful computers. This is right around the time Manin is credited with mentioning the idea of quantum computation in his book Computable and Uncomputable and before the 1981 Physics of Computation conference, which I think is rightfully considered a good point to take as the starting time for quantum computing.

The second thing that I love is Wheeler. “may in fact be time-asymmetric or an uninterrupted process of change or of cosmoplastic or cosmopoietic interadjustments and interchanges” I mean come on this is awesome who writes like that these days? Wheeler’s writing was so full of this crazy poetry, that it famously got parodied in “Rasputin, Science, and the Transmogrification of Destiny” by “John Archibald Wylers”. Excellent stuff.

I was lucky enough to work with a brilliant graduate student, Ben Toner, where we looked at the information cost of simulating entanglement. When we completed that work, Ben was able to attend a conference in honor of Wheeler, and I believe he told him about our work. I’m sad I never got to meet him, but I hope he could recognize in Ben talking with him, the long echo of his impact on those of us who still dream more about computation and the universe.

NISQ is a term coined by John Preskill¹ circa 2018 and stands for “Noisy Intermediate-Scale Quantum”. The term is aimed to describe quantum computers that were not just toy few qubit systems, but systems of a slightly larger scale. This “slightly larger” is a bit hard to define, but roughly most people take it as what is achievable with a quantum computer that does not use error correction. Or in other word the “intermediate” means roughly “what you can do with the natural fidelities of your qubits” (with a fudge factor for those who want to plug their nose and use error mitigation.)

Now this is a blog, so I will give my opinion. And that is that word intermediate in NISQ drives me nuts. I mean in part because it is vague (intermediate between what?), but more because the word itself is a disaster. Intermediate comes to us from Latin, being a combination of inter, meaning “between”, and medius meaning “middle”. But this is silly how can there be a middle without being between? It’s like saying “middle middle”. Whenever I hear NISQ I am reminded of this bastard doubling, and I start working on a time machine to go back in time and work on etymological corrections (good short story idea: a society of time travelers whose sole goal is to bring reason to the etymological record).

A more interesting question than my own personal hangups on word origins is what should we call what exists on the other side of intermediate. My friend Simone Severini has used the term LISQ which stands for “Logical Intermediate-Scale Quantum”². The idea, as I understand it, is to use this term to refer to the era where we start to construct the first error corrected quantum devices. In particular it is the place where instead of using raw physical qubits one instead uses some logical encoding to build the basic components of the quantum computer. (<high horse>Of course, all qubits are encoded, there is always a physical Hamiltonian with a much larger Hilbert space at work, what we call a qubit subsystem is a good approximation, but it is always an approximation.</high horse>). I am exciting that we are indeed seeing the ideas of quantum error correction being used, but I think this obscures that what is important is not that a qubit is use error correction, but how well it does that.

I want to propose a different acronym. Of course, I will avoid the use of that annoying term intermediate. But more importantly I think we should use a term that is more quantitative. In that vein I propose, in fine rationalist tradition, that we use the metric system! In particular the quantity that is most important for a quantum computer is really the number of quantum gates or quantum instructions that one can execute before things fall apart (due to effects like decoherence, coherent imprecision, a neutral atom falling out of its trapping potential, or a cataclysmic cosmic ray shower). Today’s best perform quantum computations have gotten signal out of their machine while reaching somewhere near the 1000 gate/instruction level³. We can convert this to a metric prefix, and we get the fine “Kilo-Instruction Scale Quantum”. Today’s era is not the NISQ era, but the KISQ era.

And as we start to move up the scale by using error correction (or somehow finding natural qubits with incredible raw fidelities) we then start to enter the regime where instead of being able to run a thousand instructions we start to be able to run a million instructions. This till be the “Mega-Instruction Scale Quantum” era or MISQ era. And I mean how cool will that be, who doesn’t love to say the word Mega (Just don’t drawl your “e” or you might stumble into politics). Then we can continue on in this vein:

• 10³ instructions = KISQ (kilo) = NISQ
• 10⁶ instructions = MISQ (mega)
• 10⁹ instructions = GISQ (giga)
• 10¹² instructions = TISQ (terra) <– Shor’s algorithm lives around here
• …

An objection to this approach is that I’ve replaced the word intermediate with the word instruction and while we gain the remove of the “middle middle”, we now the vague term instruction. The word origin of instruction is a topic for another day, but roughly it is a combination of “in” and “to pile up”, so I would argue isn’t doesn’t have as silly an etymology as intermediate. But more to the point, an “instruction” has only an imprecise meaning for a quantum computer. Is it the number of one and two qubit gates? What about measurements and preparations? Why are we ignoring qubit count or gate speed or parallelism? How do we quantify it for architectures that use resource states? To define this is to fall down the rabbit hole of benchmarks of quantum computers⁴. Benchmarking is great, but it always reminds me of a saying my grandfather used to tell me “In this traitorous world, nothing is true or false, all is according to the color of the crystal through which you look”. Every benchmark is a myopia, ignoring subtleties at the cost of quantiative precision. And yes, people will fudge any definition of instruction to fit the strengths of their quantum architecture (*ahem* algorithmic qubit *ahem*). But terms like NISQ are meant to label gross eras, and I think its okay to have this ambiguity.

One thing I do like about using the metric prefix is a particularly pressing problem. While it has been a real challenge to find NISQ algorithms that have “practical” (whatever that means⁵) an equally pressing problem is what sort of quantum algorithms will be achievable in the MISQ era. The place where we have the most confidence in the algorithmic advantage offered by quantum computers, simulation and experimental math algorithms (like factoring), lie above the GISQ and probably in the TISQ region. Roughly what we need are quantum algorithms that are linear time algorithms, so that for instances sizes becoming non-trivial (say a thousand), their total spacetime volume is a this size squared. And while there has been work on algorithms in this era, I would not say that we confidently have algorithms we know will be practically useful in MISQ. And this MISQ/GISQ gap is extremely scary!

So long live the NISQ era! And onward and up to MISQ and beyond!

1. “Quantum Computing in the NISQ era and beyond”, Preskill arXiv/1801.00862 ↩︎
2. “Bye NISQ. Hello LISQ?”, Simone Severini LinkedIn post ↩︎
3. As an example “Phase transition in Random Circuit Sampling” by the Google group (of which I’m a member) shows a signal for circuits with 32 cycles and 67 qubits. arXiv/2304.11119 ↩︎
4. A prominent benchmark is Quantum Volume, defined in “Validating quantum computers using randomized model circuits” by Cross, Bishop, Sheldon, Nation, and Gambetta arXiv/1811.12926. This is a fine benchmark modulo that because Executives at BigCo’s apparently can be fooled by log versus linear scale, they really should have taken the log of the quantity they use to define the Quantum Volume. ↩︎
5. My own personal opinion is that current claims of “quantum utility” are an oversell, or what we nowadays call quantum hype, but that is a subject for a beer at a quantum beer night. ↩︎

“I am a Quantum Engineer, but on Sundays I have principles” — John Bell, as related Nicholas Gisin in quant-ph/0104140

Ahead of his time not just on the implications of quantum theory, but also on the moral of life in the quantum industry.

“We are in a box,” says me.

“Do you see some radium hooked up to a crazy steampunk device with skulls and crossbones and yellow, definitely yellow, but maybe also neon green or wavey blue?” says Qubitslets.

“No I think we put ourselves in the box,” says me. “I don’t see any radium.”

“Maybe we’re in that branch of the wave function where we’ve transmogrified ourselves into a simulation. And we’re in a box because those post capitalists are too damn cheap to simulate us outside of a small goddamn box. Just like new Seattle townhouses. We’re in the cheap Android version of a tech bros afterlife. Do you see brass?”

“No brass,” says me, “but there is something growing in the corner.”

“A tunnel?” asks Qubitslets, “Remember that tunnel we were digging to the moon? I’ve been thinking about the replica symmetry breaking structure of our many tunnel passages to the moon. Maybe we should leverage quantum effects? Jesus, did I just say that? Have I been infected with Goldman Socks ibank spin 3/2s disease? At least I’m a fermion I guess. Not like those collective Marxist bosons over at Google Vultures.”

“I will remind you of the last time we used quantum effects,” says me. “We ended up changing the vacuum state from suck to blow. Luckily it was an unstable equilibrium, and because we are particle theorists and not cosmologists, we didn’t have to think ‘equilibrium of the Higgs-Anderson-Goldstone field with respect to what?’, so the universe just relaxed back to its current vacuum. I sure do miss the werewolves from that old vacuum, though. No, the thing growing in the corner is in a jar.”

“Crap”, says Qubitslets, “we’ve been quarantined!”

Suddenly the Medium Cryostat materializes from The Void. “There is no virus and if there were viruses they would be foreign viruses with foreign RNA and a sheath of foreignness so tricky in its conformal structure we would need a wall to stop it. Because there is no virus, which there certainly isn’t, we must build walls around us and between us and under us. The Great Walling must begin. And we must stay behind our walls and only go out to visit our grandma if she is in a nursing home but we can only do that if we test grandma for foreign viruses, which don’t exist, and, of course we must stay six feet from any particle in the universe. A foreign virus has a Compton wavelength of six feet, I am told.”

“In light of us not being afraid of viruses, because they don’t exist, we will need to plan for how The Great Economy can survive the foreign viruses, if they existed. Stock buybacks were insurance claims for the future antibodies the corporations of The Great Economy would need during The Great Walling, so we should cash out their claims. Because of the uniform structure of economic strata across our Great County, we can use the base minimum wage to pay the minimum required to sustain minimal substance for those impacted by the viruses. If the viruses existed.”

“But we must also not forget what made this a Great Country, again. Never forget the resilience of our people to the scientific method, again. Of the possibility of our citizens being able to think in terms of counterfactuals, again. And of our dedication to spring break and Easter services and a Latin homily about licentious spring breakers, which no, does not arouse the Medium Cryostat. Amen. Oops, I mean Again.”

“And because we are a generous Medium Cryostat, and we know that living behind walls is hard (but necessary because maybe viruses), we shall provide to every home everywhere a jar of Sourdough Levain. Lactobacilli and yeast for all, because nothing says that you aren’t scared of invisible microscopic viruses like cooking with a self reproducing jar of sticky goo.”

“Hooray!” says Qubitslets, “we get to bake bread!”

“Did I ever tell you about the time my girl forgot to feed the starter,” says me ,”and the starter died, and in the tears that fell into the hooch that was all that remained, I could see that the relationship was over by studying the way the waves spread and reflected off the walls of the jar?”

“I bet we can study the exponential growth of the yeast and use that to model viruses,” says Qubitslets. “As physicists we know that only simple models that use physics concepts can be used for public health decisions.”

“Or maybe in the replication of the yeast, we’ll discover that we are just cellular automata or hypergraphs transforming under some crowdsourced update rule.”

“But no brass,” says Qubitslets.

“Yeah, no brass.”

** This post is a tribute to the best blog that every was, ever will be, and ever could be. Fafblog you are greatly missed.

Is this thing on?

Can pontiffs un-retire (un-renunciate)?  I mean, I retired from being a pontiff way before it was cool.  But now the sweet siren call of trying to figure out whether there is really a there there for noisy intermediate scale quantum devices has called me back.   I think it may be time to start doing a little bit of quantum pontificating again.  My goal, as always, will be to bring down the intellectual rigor among quantum computing blogs.  And to show you pictures of my dog Imma, of course.
Cue bad joke about unitary dynamics and quantum recurrences in 3, 2, 1, 0, 1, 2, 3, …