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Network of time-multiplexed optical parametric oscillators as a coherent Ising machine


Finding the ground states of the Ising Hamiltonian1 maps to various combinatorial optimization problems in biology, medicine, wireless communications, artificial intelligence and social network. So far, no efficient classical and quantum algorithm is known for these problems and intensive research is focused on creating physical systems—Ising machines—capable of finding the absolute or approximate ground states of the Ising Hamiltonian2,3,4,5,6. Here, we report an Ising machine using a network of degenerate optical parametric oscillators (OPOs). Spins are represented with above-threshold binary phases of the OPOs and the Ising couplings are realized by mutual injections7. The network is implemented in a single OPO ring cavity with multiple trains of femtosecond pulses and configurable mutual couplings, and operates at room temperature. We programmed a small non-deterministic polynomial time-hard problem on a 4-OPO Ising machine and in 1,000 runs no computational error was detected.

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Figure 1: Principle of operation of OPO Ising machine.
Figure 2: Experimental set-up.
Figure 3: Slow detector results.
Figure 4: Fast detector results.


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The authors thank S.E. Harris, H. Mabuchi, M. Armen, S. Utsunomiya, S. Tamate, K. Yan and Y. Haribara for discussions and K. Ingold, C.W. Rudy, C. Langrock and K. Urbanek for experimental support. The work is supported by the FIRST Quantum Information Processing project.

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Authors and Affiliations



A.M. and Y.Y. conceived the idea and designed the experiment. A.M. and K.T. carried out the experiment. Z.W. performed the numerical simulations. Y.Y. and R.L.B. guided the work. A.M. wrote the manuscript, with input from all authors.

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Correspondence to Alireza Marandi.

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The authors declare no competing financial interests.

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Marandi, A., Wang, Z., Takata, K. et al. Network of time-multiplexed optical parametric oscillators as a coherent Ising machine. Nature Photon 8, 937–942 (2014).

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