Careful phasing of a photonic qubit brings light under control

Enlarge / Splitting photons up into a collection of neighboring frequencies may help with quantum computation. (credit: NIST)

Way back when I started writing for Ars, experimental quantum computing had just started to take off. At the time, the big demonstrations of quantum computation were very simple calculations, performed using single photons as repositories of quantum information. Back then, demonstrating even a single logical gate was a challenge. Light ruled the roost, and charged particles were reduced to the status of not-quantum-enough.

That changed, of course. Now, all the big demonstrations make use of charged particles: little superconducting current loops, rows of ions, or others. Light, it seems, has been reduced to a way of moving qubits between charged particles.

But a recent result shows that there is life left in photon-based quantum computers and that the degree of parallelization available to a photon-based quantum computer will be difficult to beat using other qubit technologies.