Quantum computer program developed to detect leakage of encoded information to unwanted states

University of Warwick developed program will give quantum computer users the ability to ascertain that their machines are doing precisely what they are supposed to do

Researchers from the University of Warwick claim to have developed a new quantum computer program that can detect leakage of information from the states of 0 and 1 to unwanted states.

According to the researchers, the new technology will give users the ability to check the reliability of quantum processing and to ascertain that quantum computing machines are doing precisely what they are supposed to do.

The concept of quantum computers was first theorised in 1980s, although quantum technology developed at a relatively slow pace over the past three decades.

The new technology will give users the ability to check the reliability of quantum processing

There is a fundamental difference between how quantum computers and classical computers work. In quantum computers, quantum bits (or qubits) are the basic building blocks. These qubits, which are used to store information, are described as the superpositions of '0' and '1' states.

For a quantum computer to work properly, qubits must remain 'entangled' with each other. In other words, one qubit should quickly affect another qubit, even when they are physically separated from each other.

A big challenge in terms of developing quantum computers is the "leakage" of encoded information. Leakage refers to the problem where the hardware in a quantum computer encodes the information incorrectly in another state.

Because qubits remain entangled with each other in quantum systems, even a minuscule leakage accumulating over thousands of hardware components can result in miscalculations and in collapse of the entire system.

Quantum computers are ideally made of qubits, but as it turns out in real devices some of the time they are not qubits at all

Moreover, the process of error correction comes with many flaws, and can further corrupt the encoded information contained in the qubits.

"Quantum computers are ideally made of qubits, but as it turns out in real devices some of the time they are not qubits at all - but in fact are qutrits (three-state) or ququarts (four-state systems)," said Dr Animesh Datta, associate professor of physics at the University of Warwick.

"Such a problem can corrupt every subsequent step of your computing operation."

In the current study, the researchers used the IBM Q Experience quantum devices, which are publically accessible through IBM's cloud service.

The team used the dimension witnessing technique in which some specific operation was repeatedly applied on the IBM Q platform to eventually get a result dataset.

According to the researchers, this dataset could not be explained by a single quantum bit, and a more complicated, higher dimensional quantum system was required to explain the result.

The researchers claimed that the probability that the result would arrive from mere chance was less than 0.05 per cent.

According to Dr George Knee of the University of Warwick, the dimension witnessing approach used in the study was able to demonstrate that "unwanted states were being accessed in the transmon circuit components".

The findings of the study are published in the journal Physical Review A.

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