Using wavepackets instead of photons in quantum computer

Question

Why does a photonic quantum computer require photons? Why wouldn't wave packets work just as well, better in fact since it would get away from the use of fragile single photons? (Article)

Answer 1

When using quantum optics for quantum computation, you can use also wave packets and not just single photons. There is a whole field of continuous-variable (CV) quantum computing that deals with this problem. There are both pros and cons to this approach compared to using single photons:

Pros:

• Entanglement in CV quantum optics can be generated deterministically using optical parametric amplifiers.

• Working with Gaussian wave packets is rather simple both in terms of theoretical description and experimental realization.

Cons:

• Gaussian states are not strictly orthogonal so that working with binary data will have a nonzero error rate.

• Computations with Gaussian states can be efficiently simulated using classical computers. This means that some non-Gaussian operation is required and these are usually quite demanding experimentally.