Pan Jianwei: The next quantum breakthrough will happen in five years

Recently, Pan Jianwei, Lu Chaoyang, Zhu Xiaobo, etc. from the University of Science and Technology of China, in collaboration with Professor Adán Cabello of the University of Seville, Spain, conducted the first experiment to exclude the standard quantum mechanics in the form of real numbers. The researchers used ultra-high-precision superconducting quantum circuits to achieve deterministic entanglement exchange, and proved that real numbers cannot fully describe standard quantum mechanics with an experimental accuracy of more than 43 standard deviations, establishing the objective reality of complex numbers.

Adán Cabello and Pan Jianwei in Stockholm 2019
 

On February 3, Spanish newspaper El Pais[1] reported an interview with Academician Pan Jianwei and Professor Adán Cabello.
 
The report begins with a review of the study, a collaboration between the Chinese and Spanish teams. Last year, in the journal Nature [2], a group of researchers proposed the idea that an alternative to real-number-based quantum theory could be falsified experimentally. This is a challenge posed by Pan Jianwei, a leading scientist in the quantum field, and physicist Adán Cabello of the University of Seville participated in the challenge. Their joint research demonstrates "the integral role of complex numbers (such as the square root of -1) in standard quantum mechanics." These results have led to advances in the development of computers using this technique, which, according to Cabello, "have been previously Testing quantum physics in inaccessible territory."
 
Pan Jianwei, 51, graduated from the University of Science and Technology of China in 1987 and is a doctoral candidate at the University of Vienna. He leads one of the largest and most successful quantum research teams in the world, and was called by Nobel Prize winner Frank Wilczek as "a natural a force of nature". Added physicist Anton Zeilinger, Pan Jianwei's dissertation advisor at the University of Vienna: "Without Pan Jianwei, I cannot imagine the emergence of quantum technology."
 
Jianwei Pan's leadership in this research is critical. He explained: "This experiment can be viewed as a game between two players: real quantum mechanics and complex quantum mechanics. The game is played on a quantum computer platform with four superconducting circuits. By sending Randomly measure the base and measure the outcome, and you get the game score, which is a mathematical combination of the base of the measurement and the outcome of the measurement. The rules of the game are that if the game score exceeds 7.66 points, then real quantum mechanics is ruled out, and that's what we do."
 
The experiment was carried out in collaboration between the University of Science and Technology of China and the University of Seville, and was reported by the scientific journal Physical Review Letters [2]. It aims to answer a fundamental question: Are complex numbers really necessary for a quantum-mechanical description of nature? The results rule out alternatives in standard quantum physics that only use real numbers.

Pan Jianwei at University of Science and Technology of China
 

 According to Pan Jianwei: "Physicists use mathematics to describe nature. In classical physics, real numbers seem to fully describe physical reality in all classical phenomena, while complex numbers are only sometimes used as a convenient mathematical tool. However, Whether complex numbers are needed to represent the theory of quantum mechanics is still unknown. Our results rule out a real-number description of nature and establish the indispensable role of complex numbers in quantum mechanics."
 
Cabello added: "It's not just about ruling out a particular alternative, the importance of the experiment is that it shows how a system of superconducting qubits works. It allows us to test the predictions of quantum physics that we have made so far. The experiments performed so far cannot be tested. Because they require tight control over several qubits. Now we will be able to test them."
 
"The most promising near-term applications of quantum computers are the testing of quantum mechanics itself and the study of many-body systems," said Professor Lu Chaoyang of the University of Science and Technology of China, a co-author of the experiment. The development offers a way forward and a new approach to understanding particle behavior and interactions at the atomic and subatomic level.
 
But, as with any breakthrough, opening a new path forward creates uncertainty. However, Pan Jianwei tends to focus on the positive side: "Building a practical fault-tolerant quantum computer is one of the great challenges facing humanity," he said. "I'm more concerned with how and when we're going to build one. The biggest challenge in building a large-scale general-purpose quantum computer is the presence of noise and defects. We need to use quantum error correction and fault-tolerant operations to overcome noise and scale up the system. A fidelity Logical qubits with higher degrees than physical qubits will be the next breakthrough in quantum computing and will appear in about five years. In the home, quantum computers, if implemented, will first be implemented through cloud services.”
 
The goal of having computers with millions of qubits is still a long way off. However, the findings of the Chinese and Spanish teams make it possible to expand the use of existing quantum computers and to understand physical phenomena that have puzzled scientists for years.
 
Reference link:
[1] https://english.elpais.com/science-tech/2022-02-03/jian-wei-pan-the-next-quantum-breakthrough-will-happen-in-five-years.html
[2] https://www.nature.com/articles/s41586-021-04160-4
[3] https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.128.040403