Production And Measurement Of Four Degree Of Freedom Photonic States With Correlated Photons

Darwin Cordovilla, Jae Choi


The realization of a practical quantum computer depends on the development of single and multiple qubit logic gates. However, multiple degree of freedom logic gates are difficult to demonstrate experimentally due to the complexity arising from qubit-to-qubit decoherence. Photons seem ideal candidates for qubits due to their low interaction with their environment. A combination of optical elements has been used to produce and manipulate photonic states with multiple degrees of freedom. These manipulations simulate computations with a logic-gate set comprising of photonic states. A four-degree-of freedom system consisting of correlated photon pairs produced by down-conversion, traveling through a Mach Zehnder interferometer, and interacting with wave plates and polarizers was created. The interference pattern of the photons in the interferometer was verified using coincidence-counting electronics. It was observed that when the information carried by these photons remains indistinguishable, the photons interfere with themselves. However, interference disappeared when such information was made distinguishable. Nevertheless, the interference pattern reappeared when a polarizer was placed after the interferometer. The polarizer erased the information carried by the photon’s polarization. The results from these experiments demonstrate that photonic states could be used as multiple degree of freedom qubits to perform computations and to possibly scale a quantum computer.


Photonic states, quantum computing, distinguishability

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