More than 5 seconds! The quantum state holds a record for time

◎ Science and Technology Daily reporter Zhang Mengran

According to the latest issue of Science Advances, scientists at the U.S. Department of Energy's (DOE) Argonne National Laboratory and the University of Chicago have made a major breakthrough in quantum science research: they were able to read out qubits on demand and keep the quantum state intact for more than 5 seconds, setting a new record. The qubits are made from an easily available material of silicon carbide, which is now widely used in light bulbs, electric vehicles and high-voltage electronics.

The chips used in the experiments were made of inexpensive and commonly used silicon carbide materials. Image credit: David Awschalom/University of Chicago

"It's not common to preserve quantum information on such timescales." David Oshalom, a senior scientist at Argonne National Laboratory, the project's lead researcher, said, "5 seconds is enough time to send a light signal to the moon and achieve a return." Even after nearly 40 laps around the Earth, this light still correctly reflects the state of qubits, paving the way for a distributed quantum internet. ”

For semiconductor qubits, a typical readout method is to address the qubit with a laser and measure the light it reflects back, but this process requires very efficient detection of photons. The researchers used elaborate laser pulses to add individual electrons to their qubits based on their initial quantum state (0 or 1).

The researchers said the reflected light reflected the presence or absence of electrons, and the signal increased by almost 10,000 times. "By converting a fragile quantum state into a stable electron charge, we can make state measurements more easily." With signal enhancement, we get a more reliable answer every time we check what state the qubit is in. This type of measurement is called 'single readout', and with it we can unlock quite a few practical quantum technologies. ”

With the single-shot readout method, scientists can also make quantum states as durable as possible, whereas in the past, qubits have easily lost information due to noise in the environment.

The researchers cultivated highly purified silicon carbide samples that reduced background noise that would interfere with their qubit function. Then, by applying a series of microwave pulses to the qubit, the time it takes for the qubit to hold information is extended.

Chris Anderson of the University of Chicago, co-first author of the paper, said: "These pulses decouple qubits from noise sources and errors by rapidly flipping quantum states. Each pulse is like pressing the undo button on a qubit, eliminating any errors that may occur between pulses. ”

The researchers say that by creating a qubit system that can be manufactured in ordinary electronic devices, it is expected that the future will use scalable and cost-effective technology, opening up a new avenue for innovation in the quantum field.

Editor-in-chief dots

In the quantum realm, extending coherence times has a significant impact, for example, in the future, quantum computers can use this to handle more complex operations, and quantum sensors can detect smaller signals. Today's new time record means scientists can perform more than 100 million quantum operations before the quantum state is disturbed. The ability to perform a single readout opens a new window: in the future, we can use the light emitted by silicon carbide qubits to help develop a quantum Internet, and "basic operations" such as quantum entanglement can be implemented with silicon carbide-based systems.

Source: Science and Technology Daily

Editor: Zhang Shuang

Review: Julie

Final Judgement: Wang Yu