Researchers minimize quantum back action in thermodynamic systems through entangled measurements

Researchers minimize quantum back action in thermodynamic systems through entangled measurements

Conceptual design of the quantum work and its experimental realization. Credit: Wu Kangda et al.

Led by Academician Prof. Guo Guangcan of the Chinese Academy of Sciences (CAS), Prof. Li Chuanfeng’s group and Prof. Xiang Guoyong’s group of the University of Science and Technology of China (USTC), CAS, in collaboration with theoretical physicists from Germany, Italy and Switzerland conducted the first experiment using entangled collective measurements to minimize the backaction of quantum measurement based on photonic system.

The result was published online in Physical Review Letters on November 16.

When an observable object is measured twice on an evolving coherent quantum system, the first measurement usually changes the statistical information of the second measurement because the first measurement has broken the quantum coherence of the system, which is called measure backaction.

A previous theoretical work by Dr. Martí Perarnau Llobet in 2017 pointed out that, without violating the basic requirements of quantum thermodynamics, measurement backlash cannot be completely avoided, but the degree of backlash caused by projective measurements can be reduced by collective measurement.

Based on the above theoretical research results, Prof. Xiang and the co-authors realized the quantum collective measurement and successfully observed the reduction in backaction of measurements in 2019.

Since the quantum collective measurements used in previous works were separable, a natural question may be raised: whether there are quantum entangled collective measurements that reduce backlash more than what we have achieved.

Prof. Xiang and his theoretical collaborators studied the optimal collective measurement in the two qubit system. They found that there is theoretically an optimal collective measure of entanglement, which can minimize the backaction in a two-qubit system, and the backaction can be suppressed to zero in the case of highly coherent evolution.

They then designed and implemented the entanglement measurement via photonic quantum walk with a fidelity of up to 98.5%, and observed the reduction in the response of projection measurement.

This work is important for the study of collective measurements and quantum thermodynamics. The referees called the work an important advance in the field: “The experiment has been well conducted, as the results closely follow what one would expect from an ideal implementation. Overall, I find the article a very interesting contribution to the topic of quantum. and a great combination of new theory and flawless experimental implementation. ”

The experimental demonstration of entanglement between mechanical and spin systems

More information:
Kang-Da Wu et al, Minimizing Backaction by Entangled Measurements, Physical Review Letters (2020). DOI: 10.1103 / PhysRevLett.125.210401

Provided by University of Science and Technology of China

Quote: Researchers minimize quantum back action in thermodynamic systems via entangled measurements (2020, November 23) Retrieved November 23, 2020 from

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