Photonic Quantum Computer 

The quantum computer-based in photons is more advantageous than those based on electrons. Most of the quantum computers based either on superconducting circuits or trapped ions, providers are IBM, Rigetti, Amazon, and Microsoft. Both require the working environment lower than the temperature of the universe since the thermal fluctuations may disrupt the states of the qubit. This is very challenging to hold such costly, gigantic integrated quantum systems to process at such extremely cold temperatures.

In principle, quantum computers based on photons can run at room temperature. Photons can be transmitted via optical fiber in nowadays telecommunications infrastructure. Take advantage of this technology, systems of quantum computers can be extensively connected to form a wide quantum network and even a quantum internet. With the time multiplexing architecture, photonic quantum computers can be scaled up to millions of qubits. 

Xanadu approximately doubles the number of qubits every half year. A blueprint will be released on how to scale to millions of qubits in a fault-tolerant quantum computer.

Linear optical quantum computing depends on the photons as qubits. Instruments like mirrors, beam splitters, phase shifters play an important role in manipulation. The detector can receive the pulse and read the results. The drawback is that single photons are not easy to be experimented with, it is the reason why the strategy is limited to several photons. 

To tackle this problem, Xanadu takes advantage of Heisenberg’s Uncertainty Principle, which states that measuring position with certainty implies the uncertainty in measuring its momentum of a photon. The trade-off between position and momentum is that researchers can reduce the uncertainty of the wanted variable or while ignoring the uncertainty of the variable that we don’t.

Squeezed states can be created by firing sequences of laser pulses into microchips coupled with microscopic resonators. The network of beam splitters and phase shifters will be flown to perform the desired quantum computation. Photons are traveled from chips to superconducting detectors that count the photon numbers to extract the answer to the computation. 

With the success in the implementation of quantum computing based on photons by Xanadu, it is now possible to write high-level quantum code on the cloud. The current limitation faced by the company is the superconducting photon counters, which require frigid temperatures less than 1 degree above absolute zero. However, the company also notes that a future detector may not need to work in such cryogenic temperatures.

In the past, photonic quantum computers were bound by fault tolerance and error correction. Continuous-variable quantum computing is compatible with the previous photonic approaches. 

It is envisioned that a photonic quantum computer will constitute a quantum network over a quantum internet globally. 

Reference

https://medium.com/xanaduai/on-the-road-to-room-temperature-quantum-computation-d1bd356dcf57
https://spectrum.ieee.org/tech-talk/computing/hardware/photonic-quantum
https://www.yqqlm.com/2020/10/the-worlds-first-photonic-quantum-computer-has-been-used-on-the-cloud-platform/
https://www.forbes.com/sites/moorinsights/2020/09/09/xanadu-brings-photonic-quantum-computing-to-the-cloud/?sh=6892e4e864e6
]https://www.i-micronews.com/xanadu-wins-4-4m-investment-for-photonic-quantum-computing/