A quantum battery has been built in a quantum computer, a first step in determining whether such batteries could play a role in powering future quantum technologies.
Conventional batteries store energy because their components undergo electrochemical reactions, but quantum batteries rely on quantum bits, or qubits, that undergo changes in their quantum states. Some studies have shown that using quantum in this way can lead to faster charging, but the practicality and utility of quantum batteries remain open questions.
“Many future quantum technologies will need their quantum versions of batteries,” he says Dian Tan at the Hefei National Laboratory in China. “Although significant progress has been made in the development of quantum computing, communication and sensing, the energy storage mechanisms for these quantum systems have not been fully explored.”
Tan and his colleagues built the battery using 12 qubits made of tiny superconducting circuits, each of which they could control using microwaves. Each qubit played the role of a battery cell and also interacted with its nearest neighbors.
The researchers could control these interactions, so they experimented with two different charging protocols. One mimicked how conventional or classical batteries charge, so it didn’t use these quantum interactions, but the other protocol did. The team found that by using the quantum interactions between the qubits, the battery achieved more power and faster on average.
“The quantum battery achieves a maximum power that is up to twice that of a conventional charging power,” says a member of the team Alan Santos in the Spanish National Research Council. It’s important that it works when each qubit interacts only with its nearest neighbor, he says, because that’s the standard for superconducting quantum computers, and creating more of these beneficial interactions would be practically difficult.
James Quach at the Commonwealth Scientific and Industrial Research Organization in Australia says that until now, quantum battery charging experiments have used molecules, for example, instead of parts of an existing quantum device. Quach and his colleagues previously theorized that quantum computers powered by quantum batteries could be more efficient and easier to scale up, making them more powerful. “It was a theoretical idea that we only proposed recently, but the new work could really be used as a basis to power future quantum computers,” he says.
However, an exact comparison between conventional and quantum batteries is difficult, he says Dominik Šafránek at Charles University in the Czech Republic. In his view, there is currently no obvious way to translate the measured advantages of a quantum battery into clearly useful devices.
Kavan Modi at the Singapore University of Technology and Design, says that for qubits that only interact with their nearest neighbor, his team’s mathematical work has shown that there may be only modest charging benefits that could easily be canceled out by other properties of real quantum computers, such as their noise or slow control of the qubits.
At the same time, quantum computers can be much more energy-intensive than conventional computers, so studying how energy can be transferred in them may become essential if we want to build very large quantum computers, Modi says.
Tan says he sees energy storage for quantum technologies such as quantum computers as an ideal use case for his team’s quantum battery. The researchers now want to combine their battery with a qubit-based quantum heat engine that would produce energy that could then be stored in the battery, all in a quantum computer.
topics:
- quantum computing/
- quantum physics
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