Recent Advances on All-Optical Logic Gates

Connie J. Chang-Hasnain

All-optical devices including optical buffers, wavelength converters, optical logic gates and ultra-low Vpi optical modulators can be enabled by leveraging coherent light-matter interactions to create tailorable dispersion characteristics in semiconductors. Recent advances will be discussed.

Mial E. Warren, Y. H. Lee, Greg R. Olbright +7 more

Frank A. P. Tooley

Mingna Xun, Sheng Ye, Meng Li +5 more

Compact controlled-NOT (CNOT) gates are essential for achieving large-scale quantum information processing. Recently, metasurfaces have been emerging as a promising miniaturized platform for quantum optics thanks to their advanced light field manipulation capability and subwavelength thickness. Here we report, for the first time, to our knowledge, the experimental demonstration of a quantum CNOT gate realized with a single-layer Pancharatnam–Berry phase-based dielectric metasurface. The metasurface completes the functions of three beam splitters, reducing the thickness of the logic gate to the subwavelength scale. The truth table fidelity reaches as high as 94.7% and state fidelities of the generated maximally entangled Bell states exceed 80%. This provides an ultrathin device for quantum information processing and holds promise for advancing quantum technology.

Ankur Saharia, Ravi Kumar Maddila, Jalil Ali +2 more

Thomas Stolz, Hendrik Hegels, Maximilian Winter +5 more

Optical qubits uniquely combine information transfer in optical fibres with a good processing capability and are therefore attractive tools for quantum technologies. A large challenge, however, is to overcome the low efficiency of two-qubit logic gates. The experimentally achieved efficiency in an optical controlled NOT (CNOT) gate reached approximately 11% in 2003 and has seen no increase since. Here we report on a new platform that was designed to surpass this long-standing record. The new scheme avoids inherently probabilistic protocols and, instead, combines aspects of two established quantum nonlinear systems: atom-cavity systems and Rydberg electromagnetically induced transparency (EIT). We demonstrate a CNOT gate between two optical photons with an efficiency of 41.7(4)% at a postselected process fidelity of 79(2)%. Moreover, we extended the scheme to a CNOT gate with multiple target qubits and produce entangled states of presently up to 5 photons. All these achievements are promising and have the potential to advance optical quantum information processing in which almost all advanced protocols would profit from high-efficiency logic gates.