Scientists at Harvard have developed a photon router. It helps connect quantum computers to networks using light. The photon router could make these machines work together over long distances.
The scientists have described the methods and results of this study in a paper published in Nature Physics.
The photon router is a small tool, about 2 millimeters long, shaped like a paper clip. It sits on a chip that’s 2 centimeters long. This device is a microwave-optical quantum transducer that turns microwave signals into optical signals, or light.
This transducer controls superconducting microwave qubits with light. Superconducting microwave qubits are tiny circuits that use microwave energy to process quantum information, working at very cold temperatures.. They can be in a superposition of multiple quantum states at once. This makes quantum computers based on these qubits powerful. The transducer lets light from far away control these qubits. It bridges the gap between weak microwave energy and strong optical energy.
A step toward bigger quantum systems
One big problem with quantum computers is keeping them cold. They need huge cooling machines like dilution refrigerators. These machines take up a lot of space. As quantum computers grow, they’ll need millions of qubits. Using only microwaves to control them is hard. Light, or optical photons, solves this. Photons carry information well, lose little energy, and work fast. The photon router uses this to connect qubits over long distances.
The device links a microwave resonator to two optical resonators. A resonator is a part that holds energy. The material, lithium niobate, helps energy move between them. This cuts out bulky microwave cables. The router could also read qubit states or link quantum computers. The scientists are persuaded that this is a practical way to scale quantum networks. The next goal is to share entanglement, a quantum link, between qubits using light. This invention moves us closer to powerful quantum networks.