Recently, a study published in the internationally renowned academic journal "Physical Review Letters" has attracted the attention of the industry. Foreign researchers draw on the study of quantum "anti-butterfly effect" to solve long-standing experimental problems in physics. The research establishes a method for benchmarking the performance of quantum computers and effectively reduces the interference of quantum information perturbations on computation.
This research is undoubtedly particularly important for quantum computing, which is being explored.
The quantum world does not allow the "butterfly effect"
Time travel is a popular theme in science fiction. So once we go back to the past, will the change of initial conditions have a "butterfly effect", so that the whole history will be changed?
Two foreign scientists, who are also the authors of the above study, simulated "time travel" with a quantum computer. They found: Quantum has the ability to repair itself. That is to say, at the quantum level, the "butterfly effect" does not hold.
In the research, the authors of the paper used quantum computer simulations to allow qubits to perform a "time travel" and travel back in time. In the process of "time travel", one of all qubits will be destroyed. Surprisingly, however, when all the qubits returned to the present, everything returned to normal, as if they had the ability to heal themselves.
The authors of the paper explain: On a quantum computer, it is possible to simulate the evolution of time in the opposite direction, in other words, to simulate a journey back in time. So we can go back in time, do a little damage, and go back to the present. After going through the above process, we find that the world is still fine, so there is no "butterfly effect" in quantum mechanics.
This means that this "quantum anti-butterfly effect" can be applied to information hiding hardware and quantum information device testing, where computers can hide information by transforming the initial state into a strongly entangled state. The new finding could also be used to test whether quantum processors really work on quantum principles.
The authors say their protocol quantifies information scrambling in quantum systems and unambiguously distinguishes it from false-positive signals in a noisy background caused by quantum decoherence. Using the simple, powerful protocol they developed, it is possible to determine how efficiently a quantum computer can process information. At the same time, the protocol is also applicable to information loss in other complex quantum systems. Decoherent forms of noise, when coupled with the surrounding environment, erase all quantum information in complex systems such as quantum computers.
The authors say their method exploits the "quantum anti-butterfly effect," which evolves a system forward and backward in time in a loop, so it can be applied to any system with time-reversed dynamics, including quantum Computers and quantum simulators using cold atoms.
To do this, they prepared a quantum system and subsystems that evolved the entire system forward, causing changes in different subsystems, and then evolved the system backwards in the same amount of time. The authors say that by measuring the information overlap between the two subsystems, it is possible to show how much information is retained by scrambling and how much is lost due to decoherence.
Multiple factors affect quantum computer performance
"In quantum computing, coherence is a quantum state that enables quantum computing, and decoherence refers to a state that loses that state as information leaks into the surrounding environment." Hefei Yuanyuan Quantum Computing Co., Ltd. related technical experts (below Relevant experts for short) explained to the reporter of Science and Technology Daily: qubits must maintain their coherence in order to maintain the quantum superposition state information. The process of destroying the coherence of qubits is called decoherence, and the time it experiences is called decoherence time. . The interaction of qubits with the environment is the main cause of their decoherence.
"Therefore, to prolong the decoherence time of qubits, it is necessary to effectively isolate all interactions between qubits and the environment, and only release the parts required for manipulation and reading of qubits, so that qubits can be approximated as an 'isolated system' ." The experts said.
Relevant experts told reporters that in the actual qubit system, there are many factors that cause qubit decoherence. And these factors are often interrelated, so there are frequent trade-offs in the design and manufacturing process. Some of them belong to the external environment, such as electromagnetic radiation, temperature fluctuations, and vibration; there are also factors that belong to the qubit manufacturing process, such as the two-level loss (TLS loss) caused by impurities around the qubit, and the quantum chip or package. Magnetic materials, packaging and circuit processes are not yet fully superconducting, and thermal noise generated by signals at low temperatures is added.
Relevant experts emphasized that in addition to "qubit coherence", the operation of quantum logic gates, the speed and fidelity of reading, are also important factors affecting the performance of quantum computers.
"In the limited coherence time, the faster the quantum logic gate operates, the more gates the quantum computer can execute. The higher the operational fidelity of the quantum logic gate, the smaller the calculation error rate." Relevant experts told Reporter, the bottleneck of operation speed and fidelity lies in the optimization of the circuit and the operation accuracy of the quantum measurement and control system. Circuit optimization includes the conversion and performance optimization of each level of circuit from room temperature to low temperature to the packaging box and the inside of the chip. The operational accuracy of the quantum measurement and control system depends on the internal digital-to-analog converter (DAC), the accuracy of the analog-to-digital converter (ADC), and the accuracy of microwave devices.
A Concise Method for Handling Information Disturbance
"Precisely, this research establishes a benchmark method. By measuring the value of a special observable quantity in the system, based on this measurement, it is possible to strictly and accurately distinguish quantum information perturbation processes from ordinary quantum regressions. coherent process," said the expert.
"This study once again shows that quantum information perturbation is fundamentally different from quantum decoherence effect, which further deepens our understanding of the quantum world, especially for complex quantum systems." Relevant experts said that using quantum information perturbation "anti-correlation" Butterfly effect", people can encode or hide quantum information. For example, by preparing the initial information into a highly entangled state, the information can still be well restored after experiencing environmental disturbances or even external attacks.
In addition, since the "quantum anti-butterfly effect" is a unique property of complex quantum systems, it can also be used to test whether a quantum computer follows the laws of quantum mechanics.
Relevant experts told reporters that in the early experiments, the existence of quantum information disturbance was observed by using quantum teleportation technology. "However, experiments like that rely on sophisticated and complex control of quantum systems, making them difficult to generalize."
Relevant experts said that this study proposes a very concise new method that can effectively distinguish quantum information disturbances and avoid noisy background disturbances such as quantum decoherence effects.
(Original title "There is a way to efficiently resolve the "anti-butterfly effect" of quantum information disturbances")