China set a surprising record of quantum entanglement

According to Live Science, the scientists created six special photons that stored 18 qubits (bits of quantum information). The three qubits stored in each photon are never before and it is a record for the number of qubits linked together through quantum entanglement .

So why is this remarkable?

All work that takes place on a normal computer or any device you are using to read this article works based on calculations using bits, switching between the two polarization states of a photon. (with "1" represented by horizontal polarization and "0" represented by vertical polarization). Quantum computing computers use qubits, similar to oscillations between two states but act according to the strange rules of quantum physics.

Unlike normal bits, qubits can have an unspecified state - no 1 nor 0, but can exist both states and become odd or entangled connections, thus status The state of this bit directly affects the other bit. This, in theory, allows conventional computers to perform all operations. However, currently quantum computing is testing the first stage. Scientists are still trying to do what they can in this study.

Qubit may have an unknown state.

Sydney Schreppler, a quantum physicist at the University of California at Berkeley, who is not involved in the study, said that this achievement is unlikely to be achieved because the research team at China University of Science and Technology (USTC) has decided Large quantities of qubit storage on very few photons."If the goal is to create 18" entangled "particles as previously done, it will be a slow process," she said.

Specifically, it takes a long time to create 6 particles in quantum entanglement in the previous experiment, during the computer's calculation period, the moment a new entangled process begins for each spell count. And each particle added to this entangled condition will take more time to get along than the previous one. Until one point it will become unreasonable to entangle the next 18 qubits and qubits.

Although there are many quantum experiments involving more than 18 qubits, but in those experiments, qubits are not entangled. Instead, systems only entangle some neighboring qubits for each calculation.

In an article published on June 28 in Physical Review Letters, available on arXiv server, for 6 photons to store 3 qubits in each particle, the researchers took advantage of the "degree of freedom" of photons. . When a qubit is encoded into a particle, it is encoded so that the particle can switch back and forth between states, like its quantum polarization or spin. Each of them is "degree of freedom".

A typical quantum experiment only involves a degree of freedom of all related particles. But particles like photons will have many degrees of freedom. And by coding using more than one level at a time, what researchers have done before, but not to the extreme like this, is to create a quantum system that stores more information. into less seeds.

"It's like you have six bits in your computer, but each bit triples the amount of information that can be stored and they can do it pretty quickly and efficiently," Schreppler said .

In fact, USTC researchers have succeeded in this experiment, which does not mean that quantum computing experiments elsewhere will begin to study more about the degree of freedom of particles. Photons are particularly useful for certain types of quantum operations, most importantly quantum networks, in which information is transmitted between many quantum computers. But other types of qubits, like qubits in superconducting circuits that Schreppler is developing, may not be able to perform this operation as easily.

An article raises the question whether or not all interactive qubits are equivalent, or is there a difference between qubit interactions on the same interacting particle or qubit interaction on another degree of freedom? each other or not.

The researchers said in an article that in the future this test could be applied to certain quantum calculations, although so far it has only been discussed in theory and has not yet been put into operation.