The ion-trap chip used to test a single qubit
Dr Jochen Wolf and Dr Tom Harty
A breakthrough in quantum computing has been achieved with a new record set for precise control over qubits, the fundamental units of quantum computers. This development holds the promise of reducing errors in quantum computations, provided it can be replicated on a larger scale.
Qubits in a quantum computer can be manipulated or encoded using a single-qubit gate, akin to how transistors manipulate classical bits. However, these gates often introduce errors, with failure rates as high as one in every 1000 state changes. With computations requiring millions of operations and numerous qubit gates, these errors accumulate rapidly, compromising the reliability of computations.
Molly Smith, Aaron Leu, and Mario Gely from the University of Oxford, along with their team, have developed a single-qubit gate with an error rate of just once in about 10 million state changes.
According to Leu, “The probability of this qubit making an error is three times lower than the likelihood of being struck by lightning in a year.”
The researchers created the qubit using a positively-charged calcium ion trapped above a chip. By employing well-controlled microwaves emitted by tiny components on the chip, they were able to reliably change the quantum state of the qubit using a gate.
This achievement marks a “new world record” in controlling the state of a single qubit, as noted by Daniel Slichter at the National Institute of Standards and Technology in Colorado. Jonathan Home from ETH Zurich in Switzerland also acknowledges the impressive technical advancement required to achieve such high levels of accuracy.
The success of this project can be attributed in part to the advancement in producing precisely calibrated microwaves, a technology that is crucial for conventional communication systems, as highlighted by Slichter.
While the team leveraged off-the-shelf devices for their work, they meticulously calibrated them and addressed all potential sources of error arising from the interaction between the qubit and microwaves, according to Gely.
However, to implement a quantum computing program effectively, more qubits and a different set of microwave controls governing their interactions will be necessary. As the system grows in size and complexity, the margin for error increases.
The researchers believe they can scale up to two-qubit gates while maintaining low error rates within a few years. In the interim, Smith suggests that their error characterization and mitigation efforts could benefit all researchers working on ion-based qubits.
Several companies are already producing and commercializing such qubits, which have been utilized in simulating complex quantum phenomena. The latest achievement underscores the potential of trapped-ion qubits as a leading platform for quantum computing now and in the future, as noted by Chris Langer from quantum computing firm Quantinuum.
Slichter expresses confidence in this approach to scaling quantum computers, emphasizing its compelling nature.
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