Aaronson explain qubits in the NY Times

Scott Aaronson announces his New York Times op-ed on quantum supremacy. His own personal interest in this is greater than I thought, as he says the NY Times forced him to reveal:

Let’s start with applications. A protocol that I came up with a couple years ago uses a sampling process, just like in Google’s quantum supremacy experiment, to generate random bits. ... Google is now working toward demonstrating my protocol; it bought the non-exclusive intellectual property rights last year.

He was the outside reviewer of the Google paper published in Nature. So he had a big hand in the editorial decision to say that this was quantum supremacy. Aaronson claims the credit for Google confirming that quantum computers can be used for generating random numbers. And Google paid Aaronson for the privilege.

I am not accusing Aaronson of being crooked here. I sure his motives are as pure as Ivory Soap. But he sure has a lot invested in affirming quantum supremacy based on random number generation. Maybe the Nature journal should have also required this disclosure.

He admits:

The computer revolution was enabled, in large part, by a single invention: the transistor. ... We don’t yet have the quantum computing version of the transistor — that would be quantum error correction.

So we don't have real qubits yet.

Aaronson has spent many years trying to convince everyone that there is a right way and a wrong way to explain qubits. Here is the wrong way:

For a moment — a few tens of millionths of a second — this makes the energy levels behave as quantum bits or “qubits,” entities that can be in so-called superpositions of the 0 and 1 states.

This is the part that’s famously hard to explain. Many writers fall back on boilerplate that makes physicists howl in agony: “imagine a qubit as just a bit that can be both 0 and 1 at the same time, exploring both possibilities simultaneously.”

So here is his better version:

Here’s a short version: In everyday life, the probability of an event can range only from 0 percent to 100 percent (there’s a reason you never hear about a negative 30 percent chance of rain). But the building blocks of the world, like electrons and photons, obey different, alien rules of probability, involving numbers — the amplitudes — that can be positive, negative, or even complex (involving the square root of -1). Furthermore, if an event — say, a photon hitting a certain spot on a screen — could happen one way with positive amplitude and another way with negative amplitude, the two possibilities can cancel, so that the total amplitude is zero and the event never happens at all. This is “quantum interference,” and is behind everything else you’ve ever heard about the weirdness of the quantum world.

Really? I may be dense, but I don't see that this is any better. He insists that the key is realizing that probabilities can be negative, or imaginary.

But this is just nonsense. There are no negative probabilities in quantum mechanics, or anywhere else.

We do have interference. Light does show interference patterns, as is possible for all waves. There is nothing the slightest bit strange about waves showing interference. But Aaronson insists on saying that the interference comes from negative probabilities. I don't see how that is mathematically accurate, or helpful to understanding quantum mechanics.

Perfect qubits would be amazing

The NY Times finally has an article on Google's quantum supremacy claim:

“Imagine you had 100 perfect qubits,” said Dario Gil, the head of IBM’s research lab in Yorktown Heights, N.Y., in a recent interview. “You would need to devote every atom of planet Earth to store bits to describe that state of that quantum computer. By the time you had 280 perfect qubits, you would need every atom in the universe to store all the zeros and ones.” ...

In contrast, many hundreds of qubits or more may be required to store just one of the huge numbers used in current cryptographic codes. And each of those qubits will need to be protected by many hundreds more, to protect against errors introduced by outside noise and interference.

Got that? 100 perfect qubit would give you more storage capacity than all the atoms on Earth.

But to store just one of the numbers used in crypto codes, you would need many 100s of qubits, as well as technological breakthrus to protect against errors.

The catch here is the modifier "perfect". Nobody has made any perfect qubits, or any scalable qubits, or any qubits protected against errors from outside noise and interference.

All this talk of 53 qubits is a big scam. They don't even have 2 qubits.

Many-Worlds theory is not science

More and more physicists are endorsing the Many-Worlds theory, and I have criticized them many times on this blog. Lubos Motl has also defended Copenhagen and criticized MW, and he has finally gotten to the heart of the matter.

MW is not just a goofy interpretation. It turns a good scientific theory into something that is contrary to all of science. It eliminates the ability to make predictions.

Motl writes:

Even today, almost 90 years later, the anti-quantum zealots who are still around – depending on the degree of their stupidity – argue that quantum mechanics is either wrong or incomplete. The typical complaint that "quantum mechanics isn't complete" is formulated as follows:

But the Copenhagen Interpretation fails to tell us what is really going on before we look.

Well, in reality, quantum mechanics tells us everything that is happening before the observation: nothing that could be considered a fact is happening before (or in the absence of) an observation! It is an answer. You may dislike it but it's a lie to say that you weren't given an answer!

Needless to say, the statements are upside down. The Copenhagen Interpretation provides us with a definition which questions are physically meaningful; and with the method to determine the answers to these questions (which must be probabilistic and the axiomatic framework clearly and unambiguously says that no "unambiguous" predictions of the phenomena are possible in general).

Instead, it's the anti-quantum "interpretations" of quantum mechanics such as the Many Worlds Interpretation that are incomplete because

their axioms just don't allow you to determine what you should do if you want to calculate the probability of an outcome of an observation.

In particular, the Many Worlds Interpretation denies that there's any collapse following Born's rule (an axiom) but it is rather obvious that when you omit this only link between quantum mechanics and probabilities, the Many Worlds paradigm will become unable to actually predict these probabilities. You created a hole – (because the building block looked ideologically heretical to him) someone has removed something that was needed (in the Copenhagen paradigm) to complete the argumentation that normally ends with the probabilistic prediction.

This is an actually valid complaint because the primary purpose of science is to explain and predict the results of phenomena.

That's right. And if you support MW, you abandoning the primary purpose of science. (I am avoiding the word "interpretation", because it is not really an interpretation. Calling it an interpretation is part of the hoax.)

Motl doesn't name names in this post, but an example is Sean M. Carroll. Motl probably has more distinguished physicists in mind, and doesn't want to embarrass them.

Belief in MW is a belief so goofy as to discredit whatever other opinions they might have. It is like believing in the Flat Earth, or that the Moon landings were faked.

Quantum measurement problem, explained

Dr. Bee explains the quantum measurement problem:

The problem with the quantum measurement is now that the update of the wave-function is incompatible with the Schrödinger equation. The Schrödinger equation, as I already said, is linear. That means if you have two different states of a system, both of which are allowed according to the Schrödinger equation, then the sum of the two states is also an allowed solution. The best known example of this is Schrödinger’s cat, which is a state that is a sum of both dead and alive. Such a sum is what physicists call a superposition.

We do, however, only observe cats that are either dead or alive. This is why we need the measurement postulate. Without it, quantum mechanics would not be compatible with observation. ...

Why is the measurement postulate problematic? The trouble with the measurement postulate is that the behavior of a large thing, like a detector, should follow from the behavior of the small things that it is made up of. But that is not the case. So that’s the issue. The measurement postulate is incompatible with reductionism. ...

I just explained why quantum mechanics is inconsistent. This is not a 'vague philosophical concern'.

She also says QM is incomplete.

This so-called measurement problem is a 'vague philosophical concern' in the sense that it does not present any practical difficulties.

When you say a theory is inconsistent, that usually means that it allows computing two different outcomes for some proposed experiment. That never happens with QM.

To see that there is an inconsistency, you have to wade thru a discussion of not seeing cats that are alive and dead at the same time.

It is not clear that this problem is a problem.

If anything good comes out of quantum computing research, it could be a better reductionist understanding of quantum measurement. Quantum computers seek to string together qubits as much as possible without measuring them. Because the computation depends on this lack of measurement, maybe the experiments could tell us more precisely just what a measurement is.

But the quantum computing research has told us nothing of the kind. Good old QM/Copenhagen is the underlying theory for all these experiments, and we have no clue that the 1930 theory is not good enuf.

IBM explains why Google has a quantum flop

Wired reports:

IBM Says Google’s Quantum Leap Was a Quantum Flop ...

Monday, Big Blue’s quantum PhDs said Google’s claim of quantum supremacy was flawed. IBM said Google had essentially rigged the race by not tapping the full power of modern supercomputers. “This threshold has not been met,” IBM’s blog post says. Google declined to comment. ...

Whoever is proved right in the end, claims of quantum supremacy are largely academic for now. ... It's a milestone suggestive of the field’s long-term dream: That quantum computers will unlock new power and profits ...

Wired says "academic" because everyone quoted claims that quantum supremacy will soon be achieved.

But where's the proof?

Nobody believed the Wright brothers could fly until they actually got off the ground. Quantum supremacy was supposed to be a way of showing that quantum computers had gotten off the ground. If those claims are bogus, as IBM now claims to have proved, then no quantum computers have gotten off the ground. That "long-term dream" is pure speculation.

Update: Google is now bragging, as its paper appeared in Nature. I assumed that it was trying to get into either Science or Nature, but I believe that Nature claims that it does not object to releasing preprints. If so, Google could have addressed criticisms after the paper was leaked.

Quanta mag has an article on the Google IBM dispute:

Google stands by their 10,000 year estimate, though several computer experts interviewed for this article said IBM is probably right on that point. “IBM’s claim looks plausible to me,” emailed Scott Aaronson of the University of Texas, Austin. ...

Aaronson — borrowing an analogy from a friend — said the relationship between classical and quantum computers following Google’s announcement is a lot like the relationship in the 1990s between chess champion Garry Kasparov and IBM’s Deep Blue supercomputer. Kasparov could keep up for a bit, but it was clear he was soon going to be hopelessly outstripped by his algorithmic foe.

“Kasparov can make a valiant stand during a ‘transitional era’ that lasts for maybe a year or two,” Aaronson said. “But the fundamentals of the situation are that he’s toast.”

Following his analogy, IBM's Deep Blue did beat Kasparov, but not convincingly. Maybe the computer was lucky. It was really the subsequent advances by others that showed that computers were superior.

So Aaronson seems to be saying that this research does not prove quantum supremacy, but other research will soon prove it.

We shall see.

Meanwhile, let's be clear about what Google did. It made a random number generator out of near-absolute-zero electronic gates in entangled states. Then it made some measurements to get some random values. Then it said that the device could be simulated on a classical computer, but it would take more time. Maybe 10,000 years more, but maybe just a couple of hours more.

That's all. No big deal, and certainly not quantum supremacy.

Update: Scott Aaronson weighs in , and admits that he was a Nature reviewer. He is happy because he is professionally invested in quantum supremacy being proved this way.

But he admits that Google's claim of 10k years is bogus, and that Google does not have any scalable qubits at all. Further more the researchers cooked the circuits so that they would be hard to simulate classically, while being completely useless for actually doing a computation.

To actually compute something useful, Google would need scalable qubits with some fault-tolerance system, and Google is no closer to doing that.

It has long been known that there are quantum systems that are hard to simulate. The only new thing here is that Google says its system is programmable. I am not sure why that is a good thing, as it cannot be programmed to do anything useful.

Update: Aaronson argues:

But I could turn things around and ask you: do you seriously believe at this point that Nature is going to tell the experimenters, “building a QC with 53 qubits is totally fine — but 60? 70? no, that’s too many!”

The flaw in this argument is that they don't really have a QC with 53 qubits. They have a random number generator with 53 components that act enuf like qubits to generate random numbers.

Computing something useful is expected to require 10 million real (scalable) qubits. Yes, Nature may very well say you can have a quantum device to generate random numbers, but not get a quantum computational advantage.

Indian books on Superior and Inferior

I enjoy John Horgan's SciAm columns, especially when he expresses skepticism for fad scientific work. For example, he appears to be winning a bet that no Nobel Prize will be awarded for string theory.

He has his share of goofy ideas, such as his belief in abolishing war.

His latest column is a rant against scientific work on human races, as all such work is inherently racist

But no, he was condemning Watson’s critics, whom he saw as cowards attacking a courageous truth-teller. I wish I could say I was shocked by my host’s rant, but I have had many encounters like this over the decades. Just as scientists and other intellectuals often reveal in private that they believe in the paranormal, so many disclose that they believe in the innate inferiority of certain groups. ...

I once suggested that, given the harm done by research on alleged cognitive differences between races, it should be banned. I stand by that proposal. I also agree with Saini that online media firms should do more to curb the dissemination of racist pseudoscience. “This is not a free speech issue,”

Really? Scientists and intellectuals often reveal in private that they believe in the paranormal? I doubt that.

My guess is that he is just using "paranormal" as a word to cover beliefs he does not recognize.

I am no expert in race research, but there is a lot of it, and I cannot believe it is all bogus.

I read Superior: The Return of Race Science by British journalist Angela Saini (who is coming to my school Nov. 4, see Postscript). Superior is a thoroughly researched, brilliantly written and deeply disturbing book. It is an apt follow-up to Saini’s previous book, Inferior, which explores sexism in science (and which I wrote about here and here). Saini calls “intellectual racism” the “toxic little seed at the heart of academia. However dead you might think it is, it needs only a little water, and now it’s raining.”

British? She has Indian parents, and India is famous for its racial/caste divisions. And its sexism too, for that matter.

Her books are mostly politics, not science. The favorable reviews just show how science has been corrupted. Here is how she writes:

If anything, the public debate around race and science has sunk into the mud. To state even the undeniable fact that we are one human species today means falling afoul of a cabal of conspiracy theorists. The “race realists,” as they call themselves online, join the growing ranks of climate change deniers, anti-vaxxers and flat-earthers in insisting that science is under the yoke of some grand master plan designed to pull the wool over everyone’s eyes. In their case, a left-wing plot to promote racial equality when, as far as they’re concerned, racial equality is impossible for biological reasons.

How did we get here? How did society manage to create so much room for those who genuinely believe that entire nations have innately higher or lower cognitive capacities,

Maybe because some nations have achieved much more than other nations?

What has started with a gentle creep through the back door of our computers could end, if we’re not careful, with jackboots through the front door of our homes. Populism, ethnic nationalism and neo-Nazism are on the rise worldwide.

No, this is just leftist paranoia. Neo-Nazism does not even exist, as far as I know.

Google overhyped announcement imminent

Nautilus:

News on the quantum physics grapevine, Frankfurt Institute theoretical physicist Sabine Hossenfelder tells me, is that Google will announce something special next week: Their paper on achieving quantum supremacy, the realization of a quantum computer that outdoes its conventional counterpart. ...

It’s nothing to get too excited about yet. “This” — NISQ — “is really a term invented to make investors believe that quantum computing will have practical applications in the next decades or so,” Hossenfelder says. “The trouble with NISQs is that while it is plausible that they soon will be practically feasible, no one knows how to calculate something useful with them.” Perhaps no one ever will. “I am presently quite worried that quantum computing will go the same way as nuclear fusion, that it will remain forever promising but never quite work.”

We know that the Sun gets its energy from nuclear fusion. We don't know that quantum speedups are even possible.