Floquet quantum simulation with superconducting qubits

  1. Oleksandr Kyriienko,
  2. and Anders S. Sørensen
We propose a quantum algorithm for simulating spin models based on periodic modulation of transmon qubits. Using Floquet theory we derive an effective time-averaged Hamiltonian, which
is of the general XYZ class, different from the isotropic XY Hamiltonian typically realised by the physical setup. As an example, we provide a simple recipe to construct a transverse Ising Hamiltonian in the Floquet basis. For a 1D system we demonstrate numerically the dynamical simulation of the transverse Ising Hamiltonian and quantum annealing to its ground state. We benchmark the Floquet approach with a digital simulation procedure, and demonstrate that it is advantageous for limited resources and finite anharmonicity of the transmons. The described protocol can serve as a simple yet reliable path towards configurable quantum simulators with currently existing superconducting chips.

Continuous wave single photon transistor based on a superconducting circuit

  1. Oleksandr Kyriienko,
  2. and Anders S. Sørensen
We propose a microwave frequency single photon transistor which can operate under continuous wave probing, and represents an efficient single microwave photon detector. It can be realized
using an impedance matched system of a three level artificial ladder-type atom coupled to two microwave cavities connected to input/output waveguides. Using classical drive on the upper transition, we find the parameter space where a single photon control pulse incident on one of cavities can be fully absorbed into hybridized excited states. This subsequently leads to series of quantum jumps in the upper manifold and the appearance of a photon flux leaving the second cavity through a separate input/output port. The proposal does not require time variation of the probe signals, thus corresponding to a passive version of single photon transistor. The resulting device is robust to qubit dephasing processes, possesses low dark count rate, and can be readily implemented using current technology.