Simulating quantum light in plasmas using programmable qubits

Light-plasma interactions are usually explored in the classical limit of laser light, which is a coherent state of photons. However, photons can occupy intrinsically quantum states, such as squeezed states, that are expensive to simulate using classical computers. Here, we develop a quantum model of plasma-mediated light amplification and demonstrate a two-qubit simulation on quantum hardware. Using the best-performing qubits, we show that the exact unitary, which maps initial to final states, can be realized to high fidelity. However, error mitigation is required before the quantum device can be used to simulate beyond a few time steps. We employ random compilation to suppress coherent error accumulation, such that each time step uses a different but equivalent gate sequence. Moreover, to account for decoherence, we rescale the exponentially decaying probability amplitudes using rates measured from randomized benchmarking. Finally, we reduce gate depth by merging single-qubit gates using optimal control and reducing two-qubit gate pulse duration using parametric entanglers. Using these techniques with readout error mitigation, present-day quantum hardware can advance enough time steps to capture interesting nonlinear dynamics.