PHI Lab Research/
If N degenerate OPOs are mutually coupled via optical delay line circuits or measurement feedback circuits, the phase decison process of each OPO is no more governed by spontaneous symmetry breaking, but instead N OPOs collectively pick up a unique spin configuration due to the quantum correlation among N OPOs as shown in Figure 2. We can determine the amplitudes and phases of mutual coupling constants among N OPOs in order to make the selected spin configuration be a ground state of a given Ising problem. Before the final decision is made at the threshold, N OPOs perform a quantum parallel search with their squeezed vacuum states and establish a seed for the final decision making through formation of quantum entanglement or discord between N OPOs. This is a principle of degenerate OPO based coherent Ising machines.
In general, quantum computational resources, such as superposition and quantum correlation for parallel search and quantum interference for suppressing classical chaos, lose their abilities as a dissipative coupling to external reservoirs increases, as shown in Figure 3. On the other hand, classical computational resources, such as spontaneous/collective symmetry breaking for decision making and exponential amplitude amplification of a solution state, lose their capabilities as a dissipative coupling to external reservoirs decreases as shown in Figure 3. We need the quantum and classical computational resources simultaneously in order to realize an efficient computing device. A degenerate OPO is a unique device which posesses such quantum and classical behaviors simultaneously at room temperatures.
A few topics of our current focus include:
- Entanglement and quantum discord in coherent Ising machines and XY machines
- Optical all-to-all coupling in coherent Ising machines and XY machines using Floquet engineering
- Quantum suppression of classical chaos in coherent SAT solvers
- Fig 1 Vacuum state squeezing and spontaneous symmetry breaking in degenerate OPO