Behind superconducting quantum computers that feature massive processing power, it is the ordinary optical fiber telecommunications technology. In a research initiative for optical fiber, physicists at the National Institute of Standards and Technology calculated and managed a superconducting quantum bit via light-conducting fiber in place of metal electrical wires. This paves way to pack a thousand thousands qubits into a quantum computer, and not just a few thousand.
The demonstration of the research initiative is described in the March 25 edition of Nature.
In fact, superconducting circuits is a leading technology to make quantum computers because they are reliable and are easily mass produced. Nonetheless, the superconducting circuits must operate at subzero temperatures, and programs to wire them for room-temperature electronics are complex and subject to overheating of qubits. Meanwhile, a universal quantum computer, which is expected to solve any problem is expected to need about 1 million qubits. On the other hand, conventional cryostats – the ones used in supercold dilution refrigerators that has metal wiring can support maximum only thousands.
Interestingly, optical fiber – the backbone of telecommunications network – has a plastic or glass core that can transfer high volume of light signals without transferring heat. Meanwhile, superconducting quantum computers use microwave pulses for storing and processing information. Therefore, in this structure, the light needs to be converted precisely into microwaves.
To present a solution to this, researchers at the National Institute of Standards and Technology combined the fiber with a few other standard parts that convert, transmit, and measure light at photons or single particles level, which can be easily converted into microwaves. Importantly, the system performed as well as the one with metal wiring and maintained the fragile quantum states of qubits.