Quantum Computing Hardware
Which correctly describes photonic quantum computing, which uses photons as qubits?
- APhotons are little affected by their surroundings and travel even at room temperature, but they hardly interact with each other, so two-qubit operations must be realized by methods such as probabilistic schemes combined with measurement
- BPhotons interact strongly with each other, so their biggest advantage is that two-qubit gates can be performed reliably
- CPhotons are never lost along the way, so optical loss does not need to be considered
Show answer and explanation
Answer: A. Photons are little affected by their surroundings and travel even at room temperature, but they hardly interact with each other, so two-qubit operations must be realized by methods such as probabilistic schemes combined with measurement
Photons interact little with their surroundings and travel through optical fibers and waveguides while keeping their quantum state even at room temperature, so this approach also fits well with quantum communication. On the other hand, photons hardly interact with each other, so two-qubit operations are realized by probabilistic methods that combine auxiliary photons with measurement, or by preparing an entangled state of many photons and advancing the computation through measurements. Loss of a photon is directly an error, so low-loss optical circuits and efficient single-photon sources and detectors are key. Superconducting nanowire single-photon detectors (SNSPDs), which operate at cryogenic temperatures, are commonly used as detectors, and silicon photonics fabrication technology is expected to be useful for the optical circuits.
- A. Correct. The weak interaction between photons is what makes two-qubit operations difficult.
- B. It is the other way around: the interaction between photons is extremely weak, and that is what makes two-qubit gates difficult.
- C. Optical loss is one of the biggest challenges for photonic quantum computing.