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A team of researchers claims to have demonstrated "quantum pseudotelepathy" from a game

2022-08-16T10:44:36.299Z

The experiment is based on a proposal by the Spanish physicist Adán Cabello in 2001 One of the most fascinating properties of quantum physics is entanglement. This allows an effect, such as a rotation, on one particle (often referred to as Alice) to affect another (Bob) instantly, even though they are far apart. This ability is key in one of the most potential applications of this science: computing. But its foundations are still under study. A group of Chinese researchers believ



One of the most fascinating properties of quantum physics is entanglement.

This allows an effect, such as a rotation, on one particle (often referred to as Alice) to affect another (Bob) instantly, even though they are far apart.

This ability is key in one of the most potential applications of this science: computing.

But its foundations are still under study.

A group of Chinese researchers believes they have demonstrated "quantum pseudotelepathy" in an experiment based on a game.

The work is based, according to

Science

,

on a proposal by Adán Cabello, a professor at the University of Seville, published in 2001 in

Physical Review Letters

.

Jia-Min Xu of the University of Science and Technology of China leads the latest research, titled

Experimental Demonstration of Quantum Pseudotelepathy

and also published in

Physical Review Letters

.

The test has been carried out using the

magic squares

devised in the 1990s by David Mermin, from Cornell University (New York), and Asher Peres, from the Israel Institute of Technology.

"It's not telepathy or magic, it's physical," explains Cabello.

“This is a game that is impossible to win every time unless a special form of quantum non-locality is used.

We call it all-or-nothing

non-locality

.

It has since been called pseudo-quantum telepathy, and that name has attracted a lot of attention.

The experiment uses a set of measurements discovered by Peres and Mermin, which can be placed in a 3 x 3 table and which is sometimes called the

magic square

”, adds the Sevillian professor.

Based on this proposal, Jia-Min Xu's team believes they have found one of the keys to this physics: "We have achieved a faithful experimental demonstration of quantum pseudo-telepathy through the non-local version of the Mermin magic squares game -Peres, where Alice and Bob cooperatively fill in a magic square of three by three grids.

We adopt the hyperentanglement scheme and prepare two pairs of entangled photons both in polarization freedom and in orbital angular momentum.

Our results show that quantum players can simultaneously win all games."

More information

The first networked teleportation paves the way for the quantum internet

"We're looking at something that doesn't have a classical equivalent," says University of Ottawa quantum information scientist Anne Broadbent in

Science

of pseudotelepathy.

"It's not a name that I like, but it is true that it looks like telepathy," says the researcher from Seville.

And he explains: “Imagine that Alicia [Alice in the experiments] and Benito [Bob] are isolated in different places and have no way of communicating.

In each round of the game, a referee asks them to fill in, by putting a 1 or a -1 in each box, three boxes of a table that has 3 rows and 3 columns.

Alicia has to fill in the three boxes of the row that the referee indicates and the product of her three numbers must always be 1. For example, it is okay to put 1, -1 and -1, but it is not okay to put -1, 1 and 1. Benito has to fill in the three boxes in the column indicated by the referee and the product of his three numbers must always be -1.

Neither Alicia nor Benito know which boxes the other has to fill in.

They win if they write the same number in the box common to Alice's row and Benito's column, and they lose if they write different numbers.

Without quantum physics, at best, they could win 8 out of 9 moves.

But quantum physics allows them to always win.

Without knowing quantum physics, one could conclude that Alicia and Benito are communicating telepathically.

However, the only thing they are doing is measuring systems that they prepared before starting the game.”

Approach to the Mermin-Peres magic squares game.

Cabello considers the experiment different from other non-localities.

“Normal experiments allow games to be won with greater probability than is possible without quantum physics.

However, this experiment points to a situation where the players always win.

This makes it more interesting.

[Albert] Einstein, who was a declared antagonist of quantum physics, would have been in for a surprise,” says the professor.

“Also”, he adds, “it is a more difficult experiment to do because it is not enough to use a pair of

entangled qubits

[quantum bits] in each move;

you have to use two pairs of

hyperentangled

qubits.”

Based on the approaches of the physicist from the University of Seville, Jia-Min Xu has reproduced the game and obtained a correct result in 93.84% of the 1,075,930 games played.

The victory can be considered total if the limitations of the experiment are taken into account.

Xi-Lin Wang of Nanjing University and co-author of the research believes they can "improve the quality of hyperentangled photons."

Anne Broadbent explains in

Science

that “if the game were incorporated into a program, it would allow us to check if a quantum computer is manipulating the entangled states as it should”.

Three quantum cryptography experiments

The experiment was published at the end of July after months of reviews, coinciding with a scientific boil in the quantum field.

In three articles published simultaneously (two in

Nature

and the third in

Physical Review Letters

)

,

two groups of researchers have shown the feasibility of so-called "device-independent quantum cryptography", which is the way of using quantum physics that best guarantees the secrecy of communications because, as

Antonio Acín, from the Barcelona Institute of Photonic Sciences , explains in

Physical Review Letters , users “do not need to model the devices;

they can be treated as black boxes.”

The experiments have been carried out in the UK, Germany and China and use, respectively, entangled ions, atoms and photons.

Adán Cabello highlights the progress made with this research: “The Oxford one is the best of the three experiments because it is the only one that actually manages to generate a secure key.

The one in Munich is very spectacular because it involves greater distance.

The one in China is the most interesting for the future because it is the only one that uses photons, which is what we are really going to use for real communications.”

The Sevillian physicist admits the difficulties of bringing these advances to the real world.

"But it's fantastic," he says, "that there are experiments that have managed to get to this level of finesse in reproducing quantum mechanics."

"These demonstrations are a breakthrough for cybersecurity," according to Charles Lim of the National University of Singapore, who participated in the Munich experiment, and provide security "against an adversary with arbitrary processing power or even a quantum computer." ”, adds Jean-Daniel Bancal, from the French National Center for Scientific Research (CNRS), which has participated in the Oxford experiment.

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Source: elparis

All tech articles on 2022-08-16

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