Yale Physicists Track Quantum Errors in Real Time

Scientists at the Yale University have shown that it is possible to track quantum errors in real time. The research could advance quantum computing.

Quantum computers could change the way we compute, by allowing faster computing and large storage space. However, information loss is one of the biggest obstacles in making quantum computers a reality. The study is published in the journal Nature.

"Ninety-nine percent of quantum computing will be correcting errors," explained Yale physicist Rob Schoelkopf, Sterling Professor of Applied Physics and Physics, according to a news release. "Demonstrating error correction that actually works is the biggest remaining challenge for building a quantum computer."

What are Quantum Computers?

Current computers use 0 and 1 to store information or data. Quantum computers rely on quantum bits or qubits, which can exist as 0, 1 or any state in-between (superposition state). A quantum state is when the qubit exists as 0,1 or in a superposition state simultaneously. According to researchers, any change in the quantum system can lead to the qubit reversing to classical states of 0 or 1, which could lead to information loss.

The experiment                                                                                           

Now, researchers at Yale have shown that it is possible to track information loss in a quantum computer.

Tracking quantum computing errors is problematic because the superposition states are so fragile that any external disturbance could lead to more loss of information.

In the present research, the team used ancilla or a more stable reporter atom that detected errors in the system without actually disturbing any qubits.

During the experiment, researchers used a superconducting box. The box had the reporter atom as well as an unknown number of photons, which were cooled to about negative 459°F, a fraction of a degree above absolute zero. The cooling minimized the number of quantum errors. Researchers then assessed whether any photons left the box. Escaped photons are considered to be loss of information or a quantum error.

Ancilla - the reporter atom - helped scientists find whether there were quantum errors. Researchers said that ancilla just reports photon parity - whether there was a change from even to odd/odd  to even photons in the box - and not exact numbers. A major advantage of using the reporter atom is that it tracks the errors in real-time without disturbing the system.

Now that researchers have found how to spot errors, they hope to find a way of fixing them.

"It is hard to estimate how long it will be until we have functional quantum computers," Schoelkopf said, "but it will be sooner than we think."