Evrim Yazgin
Cosmos science journalist
Physicists at the University of Oxford, UK have set a new world record for accurately controlling a single quantum bit as part of global scientific efforts to create useful quantum computers.
The new level of accuracy is nearly 7 times greater than the previous record (achieved by the same team in 2014) and is reported in the Physical Review Letters. The Oxford team performed a quantum logic operation with errors occurring just 0.000015% of the time, or 1 error in 6.7 million operations.
In other words, an error in this experiment is more than 5 times less likely than a person getting struck by lightning (1 in 1.2 million).
Quantum bits are more prone to errors due to the noisiness of quantum mechanical systems. They are still a long way off the accuracy of modern classical computers – an average Central Processing Unit (CPU) has an error rate of just 0.000000000000001% per operation or an error every 100 trillion operations.
The new record brings physicists and engineers a step closer to quantum computers with error rates low enough that they can be relied upon to do useful calculations.
“As far as we are aware, this is the most accurate qubit operation ever recorded anywhere in the world,” says co-author David Lucas, from Oxford’s Department of Physics. “It is an important step toward building practical quantum computers that can tackle real-world problems.”
“By drastically reducing the chance of error, this work significantly reduces the infrastructure required for error correction, opening the way for future quantum computers to be smaller, faster, and more efficient,” says co-lead author Molly Smith an Oxford graduate student.
“Precise control of qubits will also be useful for other quantum technologies such as clocks and quantum sensors.”
The team’s quantum bit, or qubit, is a trapped calcium ion. Physicists usually use lasers to control the quantum state of the qubit. The Oxford team used microwaves instead, offering greater control and a cheaper, more robust set up.
While an important step forward, the experiment is still a long way off what is required for practical quantum computing.
A useful quantum computer will need more than a single qubit – hundreds, thousands or millions of qubits will be needed to work in tandem – compounding the quantum noise that leads to errors. The current record for a 2-qubit logic gate is 1 error every 2,000 operations.
