A quantum bit inspired by Schrödinger’s cat can resist making errors for an unprecedentedly long time, which makes it a candidate for building less error-prone quantum computers
By Karmela Padavic-Callaghan
6 May 2024
An artist’s concept of a quantum computer
sakkmesterke / Alamy
A quantum bit inspired by Schrödinger’s cat has managed to resist making errors for an unusually long time in a quantum computing experiment. This may make it a promising building block for more reliable quantum computers in the future.
Researchers have long believed that quantum computers can solve problems that are impossible for conventional computers, but there have been very few demonstrations of such capability so far. This is because quantum computers tend to make errors as they compute, but building a quantum computer powerful enough to correct its own errors is technically difficult.
Zaki Leghtas at the École Normale Supérieure in France and his colleagues, in collaboration with the quantum computing start-up Alice & Bob, have now created a quantum bit, or qubit, that avoids making a particularly common type of error for the unprecedentedly long time of 10 seconds.
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They made their qubit by trapping light in a small hole on a chip filled with tiny circuits made from perfectly conducting – or “superconducting” – wires. The light could oscillate back and forth in two different ways inside the hole. But instead of forcing it to oscillate one way only, the team made it do both – creating a quantum superposition similar to the one involving the cat in Erwin Schrödinger’s famous thought experiment. This type of qubit is, accordingly, called a “cat qubit”.
Leghtas says that for more than 10 years, physicists have theorised that cat qubits should be particularly unlikely to make so-called bit-flip errors, which are equivalent to the digital 0s in a conventional computer spontaneously becoming 1s, or vice versa. But demonstrating that cat qubits in the lab are so resistant to bit-flips is not straightforward.