Researchers achieve time reversal in quantum systems

Experimental setup of the superposition of the quantum evolution and its inverse evolution. Credit: Prof. Li Chuanfeng’s team

A team of researchers has made a significant breakthrough by demonstrating time reversal in a quantum system using a photonic setup.

Their work, recently published in Physical Review Letters, shows how they created a coherent superposition of quantum evolution in two opposite directions, which is a big step forward in understanding input-output indefiniteness.

In everyday life, we see time as moving from the past to the future, but in the microscopic world of quantum mechanics, the rules are different.

The fundamental equations of both classical and quantum mechanics are reversible, meaning they don’t prefer one direction of time over another. This concept is known as time reversal symmetry.

Time reversal is of great interest in quantum information science because it has applications in multi-time quantum states, simulating closed timelike curves, and reversing unknown quantum processes.

However, achieving time reversal in experiments has been challenging.

To address this, a team led by academician Guo Guangcan, along with Professors Li Chuanfeng and Liu Biheng from the University of Science and Technology of China (USTC), and Professor Giulio Chiribella from the University of Hong Kong, developed a method to simulate time reversal in quantum systems.

They did this by focusing on the input-output relationship of a quantum device.

In their experiment, the team swapped the input and output ports of a quantum device. This swap created an evolution that met the time-reversal properties of the original process, effectively simulating time reversal.

They then went a step further by quantizing the direction of evolution time, creating a coherent superposition of both forward and reverse evolutions. This approach allowed them to study the system using quantum witness techniques.

The results were impressive. By quantizing the time direction, the researchers significantly improved their ability to identify quantum channels.

They were able to distinguish between two sets of quantum channels with a 99.6% success rate.

In comparison, using a traditional approach with a definite time direction, the success rate was only 89% with the same resources.

This study highlights the potential of input-output indefiniteness as a valuable resource in advancing quantum information and photonic quantum technologies.

The ability to reverse time in a quantum system opens up new possibilities for understanding and manipulating quantum processes, which could lead to significant advancements in technology.

In summary, this research demonstrates that by using a novel method to simulate time reversal, scientists can achieve greater precision in quantum channel identification.

This finding is a major step forward in quantum technology, offering new insights and tools for future developments in the field.

Source: KSR.