Photon to photon connectivity as qubits. Very challenging, but there is plenty of good news.
The lack of deterministic photon-photon interactions is a challenge for quantum computation in this approach. Currently, the biggest challenge with this approach is lack of deterministic photon-photon interaction. It means it is hard to do gates. But, there is good news.
To deterministically control an optical signal with a single photon requires strong interactions with quantum memory. Nanophotonic structures coupled to quantum emitters may offer an attractive approach to realize single-photon nonlinearities in a compact solid-state device. "
There has been some successful research conducted at the University of Maryland and the Joint Quantum institute in controlling photons with solid-state qubits - the first single-photon switch and transistor enabled by solid-state quantum memory using a semiconductor chip.
It is alike a photon switch board, the device allows one photon to switch other photons, and hence to produce strong and controlled photon-photon interactions.
A nanophotonic cavity coupled to a spin qubit combined together, form a semiconductor membrane with quantum dots. Together they sit in the middle of the array.
The nanophotonic cavity idea first introduced by Duan and Kimble. See the document here
The array forms a photonic crystal, which uses the Bragg reflection mechanism (gives the angles for coherent scattering of waves from a crystal lattice) where light bounces around a trap. Next is quantum dots store the information about the photon with a single electron, which has the spin properties. Therefore using this switch or transistor, we can build and do gates for computation.
A scalable device suitable for quantum information processing will require higher efficiencies, as photon loss constitutes a dominant error source for photonic qubits.
Download another source of information on photon loss here:
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