The Institute of precision measurement of the Chinese Academy of Sciences confirmed that the real quantum system has the limit of manipulation speed
Recently, the Feng mang research team of Precision Measurement Institute, in cooperation with Zhengzhou University, Guangzhou Institute of industrial technology, Henan University and other units, designed and experimentally demonstrated a controllable quantum nonequilibrium thermodynamic process by using the quantum simulation experimental platform constructed by ultracold 40Ca + ions, At the single-atom level, the new quantum thermodynamic characteristic of "the manipulation speed of the quantum system far from the equilibrium state is subject to the entropy generation rate of the system" is verified with high precision for the first time. The research results are published in the top journal of physics "physics review express" Come on. This achievement not only involves the basic problems of quantum mechanics and thermodynamics, but also is of great significance for optimizing quantum technologies such as quantum measurement, quantum state preparation, and quantum information reading, and even accelerating the speed of quantum computing. It was selected as the highlight of the paper by the editorial department as "Editors' suggestion" and "characteristic in physics". The American Physical Society (APS) also reported and commented on this work with the title of "speed limit of change" as the focus on its website physics.
Using a supercomputer to simulate the real process of the real world is a method widely used in scientific and technological circles and industry. For example, the performance test of aircraft and automobile and nuclear explosion test can be simulated on supercomputers. However, when these supercomputers are used to study the quantum processes in the micro world, the original powerful computing power immediately becomes stretched. At present, the most powerful computer can only calculate the system composed of more than 30 qubits. Richard Feynman, a famous physicist, realized this difficulty in the 1970s and came up with a solution to "create an artificial quantum mechanical system to simulate real quantum processes", which is called quantum simulation. A quantum simulator is actually a simplified version of a quantum computer.
For a long time, whether we can further speed up the manipulation of quantum systems is not only a technical challenge, but also a frontier issue of basic science. The actual quantum manipulation is inevitably affected by the environment. The resulting noise will affect the fidelity of quantum manipulation, but on the other hand, this influence can play a positive role in quantum manipulation and preparation of quantum initial states. Therefore, in addition to the improvement of quantum technology, the rapid manipulation of quantum states of real systems also needs to consider other non quantum factors. A theoretical study in 2020 abstracted the above problem as a non-equilibrium thermodynamic problem and obtained a universal inequality relationship (called "dissipation time uncertainty relationship"), indicating that the evolution speed of physical system in any non-equilibrium thermodynamic process will be limited by the flow rate of entropy. Since this restriction is also applicable to quantum systems, it is not only an in-depth understanding of the basic theory of quantum mechanics, but also the first time to associate quantum velocity with thermodynamic processes.
In this work, researchers work together to test the above theoretical conclusions by using ion trap quantum manipulation technology. Ion trap system is famous for being isolated, clean, accurate and controllable. It is one of the most promising candidates to show the advantages of quantum technology. Feng Mang's research team has been developing the key technology of precision manipulation based on 40Ca + ions, aiming to develop the application technology of quantum precision measurement and explore the unknown field of the quantum world by using quantum simulation. Based on the quantum simulation experimental platform constructed by a single supercooled 40Ca + ion, the researchers skillfully designed four independently controllable dissipation channels. Each channel can be switched on and off independently, and the speed of thermodynamic process can be controlled accurately; At the same time, the researchers also independently developed a set of theoretical methods of data post-processing, so that the details of the whole thermodynamic process can be accurately presented through experimental measurement and numerical processing, which fully meets the physical conditions for simulating a controllable quantum nonequilibrium thermodynamic process. After many experiments under different parameter conditions and repeatedly comparing the measurement results, the researchers finally confirmed that the "dissipation time uncertainty relationship" is fully established in the quantum system.
This research work is helpful to understand the speed limit of real quantum manipulation, further optimize quantum technologies involving non-equilibrium thermodynamic processes such as quantum measurement, manipulation and quantum information reading, and prove once again the unexpected role of thermodynamics in real quantum processes. Especially important, this work shows that the quantum simulator composed of a single ion can accurately and reliably simulate the quantum nonequilibrium thermodynamic processes that are difficult to be observed, which once again shows the great potential of quantum technology and the future prospect of quantum technology as a subversive technology.
In 2018, Feng Mang's research team used the quantum simulation platform to verify the applicability of Randall's principle (one of the important principles in the field of Informatics) in the quantum field. The experimental data showed that the quantum perpetual motion machine could not exist; It also shows that although quantum technology is helpful to information processing, it has no advantage in energy saving. This work is once again related to the energy consumption of quantum technology. It is proved that the speed of reading quantum information will depend on the change of entropy of the system, which provides a theoretical explanation for the energy consumption required to improve the efficiency of precision measurement technology and quantum manipulation.
The research was supported by the national key R & D program of the Ministry of science and technology, the National Natural Science Foundation of China and the major special projects of the R & D program in key areas of Guangdong Province.
The left and right figures show two channels respectively. Each channel can be switched on and off independently, the speed of thermodynamic process can be controlled accurately, and the details of the whole thermodynamic process can be accurately presented through experimental measurement and numerical processing.
The above figure shows the experimental results of the 40Ca + ion quantum simulator. The dotted line is the lower limit of the uncertainty relationship. The data points of all four measured channels (marked with four colors) are above the dotted line, indicating that the dissipation time uncertainty relationship is established.
Link:
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.128.050603
https://physics.aps.org/articles/v15/17
