Studies on quantum physics are one of the issues that the new age of science focuses on the most. Quantum computers are thought to have robust communication networks that will contribute to cybersecurity or have the capacity to accelerate new drug discovery. Storing quantum information in such new application areas will require a quantum version of a computer bit known as a qubit. However, researchers are still grappling with reading problems of the information stored in these qubits. It struggles with the short memory duration or coherence of qubits, which are often limited to microseconds or milliseconds. For this reason, the "5 Second Record in Quantum State" study, which is the subject of our article, took its place in the records as an exciting development.
A team of researchers at the U.S. Department of Energy's (DOE) Argonne National Laboratory and the University of Chicago have made two major breakthroughs in tackling these common challenges for quantum systems.
On request they were able to read their qubit and then managed to maintain the quantum state for more than five seconds.
It went down in history as a new record for this class of devices. It's also worth noting that the researchers' qubits are made of an easy-to-use material called silicon carbide, which is commonly found in light bulbs, electric vehicles, and high-voltage electronics.
David Awschalom of the Argonne National Laboratory and Liew Family, Professor of Physics at the University of Chicago, are the project's principal investigators.
By creating a qubit system that could be widely used in the electronics industry, the researchers hope to open a new avenue for quantum innovation using technology that is both scalable and cost-effective.
"This essentially highlights silicon carbide as a quantum communication platform," said University of Chicago graduate student Elena Glen, researcher and lead author of the paper. “This is exciting because we already know how to make useful devices with this material, so it's easy to scale up,” he adds.
Use of Silicon Carbide Qubits
Every computer needs a method to read the information encoded into its bits.
The typical reading method for semiconductor qubits, such as those measured by the team, is to treat the qubits with lasers and measure the light emitted back. But this procedure is challenging because it requires very efficient detection of single particles of light, called photons.
Instead, the researchers use carefully designed laser signals to add a single electron to their qubit, depending on the initial quantum state, either zero or one. Afterwards, the qubit is read with a laser, as before.
"Only now, the emitted light tells us with almost 10.000 times more signal that the electron is present or not," said Glen.
“By transforming our fragile quantum state into stable electronic charges, we can measure our state much more easily. With this signal boost, we can get a reliable response every time we check what state the qubit is in. This kind of measurement is called a 'one-shot reading' and with it we can unlock many useful quantum technologies.”
Detection of Quantum States
Using the one-shot reading method, scientists can focus on maintaining quantum states for long periods of time. Since it is also known that qubits easily lose their information due to the noise in their environment, this stage is really a great progress.
The researchers produced highly purified silicon carbide samples that reduce background noise that tends to interfere with qubit operation. Next, they sent a series of microwave signals to the qubit, extending the time that their qubit retained its quantum information, in a way keeping the information consistent.
"These signals rapidly reverse the quantum state, isolating the qubit from noise sources and errors," said Chris Anderson of the University of Chicago.
The researchers think even longer consistency should be possible. Extending the coherence time has important implications, such as how small a signal a quantum sensor can detect, given how complex a future quantum computer can handle.
“For example, this new record time means that more than 100 million quantum operations will take place before our quantum state breaks down,” Anderson said. The researchers see multiple potential applications for the techniques they've developed.
“The ability to do one-shot reading unlocks a new opportunity,” Glen said. "Using the light emitted from silicon carbide qubits to help develop a future quantum internet."
“Basic operations such as quantum entanglement, where the quantum state of one qubit can be known by reading the state of the other, will now be possible on boards for silicon carbide-based systems.”
“Basically, the transformation from quantum states, which is the language of classical electronics like your smartphone, into the field of electrons, has taken place,” Anderson says.
“Next generation devices are being considered, which are sensitive to single electrons but also host quantum states. Silicon carbide can do both, and so we really see great hope for the future.” said.