Recently, scientists have made a major breakthrough in quantum research: reading quantum bits on demand for the first time and keeping the quantum state for more than 5 seconds.
Quantum technology has brought hope to many technological applications, such as the establishment of communication networks against hackers, and quantum computers that can accelerate the invention of new drugs. Quantum computers run qubits that can store quantum information.
However, scientists are still committed to studying how to easily read the information stored in qubits and increase the storage time of quantum information (that is, the coherence time of qubits is usually limited to microseconds or milliseconds).
Researchers at Argonne National Laboratory of the U.S. Department of energy and the University of Chicago have made two major breakthroughs in such research: they have realized the readout of quantum bits on demand and kept the quantum state for more than five seconds, setting the most Shanghai New World Co.Ltd(600628) record. In addition, the researchers’ qubits are made of cheap and commonly used silicon carbide materials, which can be widely used in bulbs, electric vehicles and high-voltage electronic devices. Relevant achievements were recently published in science advances.
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The picture is from science advances
“10000 times enhanced signal”
The researchers’ first breakthrough was to make silicon carbide qubits easier to read.
Every computer needs a way to read information encoded into bits. For semiconductor qubits, a typical readout method is to address qubits with a laser and measure the reflected light. But this process needs to detect photons very effectively.
Using carefully designed laser pulses, the researchers add a single electron to the qubit according to the initial quantum state (0 or 1) of the qubit, and then read the qubit with a laser.
The researchers said whether the reflected light was almost 10000 times stronger. Elena Glen, the first author of the paper and a graduate student at the University of Chicago, “By converting fragile quantum states into stable electronic charges, we can make state measurement easier. Through signal enhancement, we can get a reliable answer every time we check what state the qubit is in. This type of measurement is called ‘single reading’. With it, we can unlock many useful quantum technologies.”
With the help of single readout method, scientists can also make quantum states as long as possible. In the past, quantum bits were easy to lose information due to environmental noise.
For this purpose, researchers cultured highly purified silicon carbide samples to reduce the background noise interfering with its qubit function. Then, a series of microwave pulses are applied to the qubit to prolong the time of storing information. Prolonging the coherence time of quantum bits plays an important role. For example, quantum computers can process very complex operations in the future, or quantum sensors can detect extremely small signals.
“These pulses decouple qubits from noise sources and errors by rapidly flipping quantum states,” said Chris Anderson, co-author of the paper. “Each pulse is like pressing the undo button on qubits, eliminating any errors that may occur between pulses.”
“quantum state held for more than 5 seconds”
The researchers said that the current record of quantum state for more than five seconds means that more than 100 million quantum operations can be performed before the quantum state is disturbed.
“It is very rare to preserve quantum information on such a time scale.” “Five seconds is enough to send the speed of light signal to the moon and return. Even after nearly 40 circles around the earth, this light can correctly reflect the state of qubits, paving the way for the manufacture of distributed quantum Internet,” said David awschalom, senior scientist at Argonne National Laboratory and lead researcher of the project
Researchers believe that this research brings silicon carbide to the forefront of quantum communication platform. Because silicon carbide is cheap and commonly used, it is easy to be used in a variety of devices, so silicon carbide materials help to expand the scale of quantum networks.
Scientists also saw a variety of potential applications for the study.
“The ability of single readout opens up a new opportunity: using the light emitted by silicon carbide qubits to help develop the future quantum Internet,” Glen said. “Basic operations such as quantum entanglement, one quantum state can be understood by reading another quantum state, which has now been realized in silicon carbide systems.”
Researchers have basically completed a converter that can convert quantum states to the electronic field. “We want to create a new generation of devices that are sensitive to individual electrons and accommodate quantum states. Silicon carbide can do both, which is why we think it has a future.” Anderson said.
Researchers believe that by creating a quantum bit system that can be manufactured in ordinary electronic devices, it is expected to use scalable and cost-effective technologies to open up a new way for innovation in the quantum field in the future.
