Quantum supremacy?

A Wafer of the D-Wave Quantum Computer.
By Steve Jurvetson from Menlo Park, USA

We have been speaking about quantum computers for a few decades. These computers would work with qubits (quantum bits) instead of bits, and would perform certain operations much faster than ordinary computers.

It has been known since the thirties that quantum computers cannot solve problems that cannot be solved by ordinary computers. Those problems are called non-computable. What they would do, in principle, is solve certain problems (not all) much faster than ordinary computers. That higher speed, which in some cases should be enormous, is called quantum supremacy.

Let's give an example: we know that the decomposition of a composite number into its prime factors can be difficult. It’s trivial if the factors are small, but if the composite number is the result of multiplying two prime numbers of 100 digits each (for example) it is almost impossible to break it down, if we don’t know ay least one of the prime numbers.

The heralded pandemic

SARS-CoV-2

The November 2005 issue of Scientific American published an article signed by W. Wayt Gibbs and Christine Soares titled Preparing for a Pandemic. The article had the following subtitle-summary:

One day a highly contagious and lethal strain of influenza will sweep across all humanity, claiming millions of lives. It may arrive in months or not for years--but the next pandemic is inevitable. Are we ready?

Fourteen years later, the pandemic is here, although the authors were mistaken in one detail: they thought it would be caused by the influenza virus, but it was actually a coronavirus. These viruses belong to two different families:

Scientific models: adjustment or validation?

Leonard Nimoy
as Mr. Spock

One of the ways in which science advances is by building models, which are often made up of more or less complex sets of mathematical equations, and trying to verify whether or not these models adapt to the functioning of the real world, as described by our senses and our instruments.

When building and using a model we must consider two distinct phases:

• Model adjustment: it consists of assigning values ​​to the parameters of the model to ensure that it fits the data we already have about the real world. A model not adjusted to such prior knowledge would be totally useless.
• Model validation: it consists of using the model to make surprising predictions that nobody could have foreseen without the help of the model. If these predictions are confirmed, they become surprising accurate predictions, validating the model. However, the validation is never final, for a new surprising inaccurate prediction could invalidate it in the future.

Let's look at a few examples:

Is there energy in the cosmos?

Georges Lemaître

During the 1950s two cosmological theories entered in competition: the Big Bang, proposed by Georges Lemaître, and the steady state, proposed by Hermann Bondi and Thomas Gold. Although the second had to renounce the principle of the conservation of energy, the most sacred of physics, atheist cosmologists preferred it to the Big Bang, as it seemed to them that this theory required to accept God's creation. In the words of the English astronomer Raymond Littleton, in his popularization book The Modern Universe (1956):

A theory such as this [the Big Bang] that puts back creation to a singular instant in the remote past... to some minds it is an objection that it would imply the removal of the question of the origin of the material of the universe from the realm of science... This consideration does not of course mean that the explosion theory is necessarily wrong, but it puts the act of creation, as we might name it, beyond the reach of science.

In other words: Raymond Littleton objects to the Big Bang theory because it could force us to recognize the existence of a creative God. It cannot be said more clearly.

4 clarifications about the history of the universe

James Peebles

Certain statements by James Peebles, recent Nobel Prize in physics, have aroused controversy, although what he said is not something new, as theoretical physicists have long been saying precisely the same thing.

The Big Bang theory was proposed in 1931 by Georges Lemaître, by extending to the past the Hubble-Lemaître law. In 1948, Ralph Alpher and Robert Herman predicted that, if the Big Bang theory is correct, there must be a cosmic background radiation with a temperature close to 5 Kelvin. In 1965 Arno Penzias and Robert Wilson discovered the existence of such cosmic radiation, whose temperature proved to be 2.72548 Kelvin. The temperature is exactly the same in all directions, except for two effects that cause small differences, but never affecting more than the third decimal place.

Synthetic life, is it possible?

Frankenstein's monster

In the previous two posts in this series we have seen that the generation of synthetic life in the laboratory is probably a process more difficult than some optimists imagine.

Let’s look at one of the latest experiments in synthetic biology: George Church and Nili Ostrov, Harvard biologists, are trying to build a strain of the bacterium Escherichia coli immune to all existing viruses. How? By changing its genetic code so that viruses do not understand it and cannot use the bacterial cellular machinery to reproduce. Since the genetic code is redundant, it is possible to replace one of the codons encoding the amino acid arginine (AGA) with another that also encodes the same amino acid (CGC), and all the genes of the bacterium would go on generating the same proteins. This would be done with several rare codons. But since viruses would continue to use the substituted codons, the bacterial cell machinery would no longer be able to understand the DNA of the virus. This part of the job is almost finished. When it is done, it would also be necessary to eliminate the transfer RNAs of the missing codons and ensure that they are not remanufactured, so that the cellular machinery can no longer use them.

Note that the work done so far is the manipulation of the data recorded in the DNA. It is equivalent to changing the information contained in the hard disk of a computer so that it stops using a certain instruction of the language of the machine, by replacing it with another equivalent instruction. We are still very far from synthetic biology in the strict sense. Will it be possible to synthesize life in the near future?

Synthetic life, near or far?

In the previous post I detailed some recent advances in the field of synthetic biology, and asserted, without saying why, that I don’t think the goal of creating an artificial living cell is as near as some optimistic researchers believe, such as Craig Venter.

To explain why, I’ll make a comparison between a living cell and one of our most complex artifacts: the computer. A computer consists of the following two main parts:

1. CPU (central processing unit): as its name indicates, it’s the control center and the place where programs are executed. One of its fundamental elements is the machine language, a relatively complex binary code that the circuits of the unit interpret and execute. Every program, in order to run, must be written in machine language.
2. Memory. There are several types: hard disk, which stores the programs and data accessed by the computer, including the operating system, although many of them will never be used; cache memory, faster than the hard disk, which stores those programs and data currently being used, to speed up their process; external memories (such as flash memory), used to transmit data and programs from one computer to another, or to save copies in case of loss of information.