Shielding a fragile qubit
Physicists at Harvard University have found that a steady stream of sound waves can shield a fragile quantum bit, or qubit, from its own noisy surroundings. The method nearly triples the time the qubit can hold information.
Qubits are the basic units of quantum computers. They are extremely sensitive to heat, vibration and stray electromagnetic fields. Any disturbance can erase the information they hold. Protecting qubits from noise is one of the hardest problems in quantum computing, and it has limited the size and reliability of quantum machines for years.
How sound helps
The Harvard team used a continuous stream of acoustic waves, in effect a sound shield, around the qubit. The sound waves create a protective barrier that blocks noise coming from the environment. The idea draws on techniques used in mechanical engineering to dampen vibrations in sensitive instruments.
The researchers tested the approach on a silicon-vacancy spin in diamond, a type of qubit used in many quantum experiments. With the sound shield on, the qubit kept its information for nearly three times longer than without it. The team described the work in a paper released this month.
A path to sound-based quantum networks
The result opens a route toward quantum networks that use sound instead of light to link chips. Sound waves travel slowly, which can be useful for storing and processing quantum information on a chip. This matters for building larger processors, where qubits must stay coherent long enough to finish complex calculations.
The work also supports hybrid quantum systems that combine different kinds of qubits. Each qubit type has strengths and weaknesses. Sound-based protection could let researchers mix them without losing stability.
The team says the approach is still in the laboratory stage. More work is needed to scale it to larger quantum processors and to test it with other qubit materials. Still, the finding gives quantum engineers a new tool for a problem that has slowed the field for years.