S. Zeytinoglu

Microwave-Induced Amplitude and Phase Tunable Qubit-Resonator Coupling in Circuit Quantum Electrodynamics

  1. S. Zeytinoglu,
  2. M. Pechal,
  3. S. Berger,
  4. A. A. Abdumalikov Jr.,
  5. A. Wallraff,
  6. and S. Filipp
In the circuit quantum electrodynamics architecture, both the resonance frequency and the coupling of superconducting qubits to microwave field modes can be controlled via external
electric and magnetic fields to explore qubit — photon dynamics in a wide parameter range. Here, we experimentally demonstrate and analyze a scheme for tuning the coupling between a transmon qubit and a microwave resonator using a single coherent drive tone. We treat the transmon as a three-level system with the qubit subspace defined by the ground and the second excited states. If the drive frequency matches the difference between the resonator and the qubit frequency, a Jaynes-Cummings type interaction is induced, which is tunable both in amplitude and phase. We show that coupling strengths of about 10 MHz can be achieved in our setup, limited only by the anharmonicity of the transmon qubit. This scheme has been successfully used to generate microwave photons with controlled temporal shape [Pechal et al., Phys. Rev. X 4, 041010 (2014)] and can be directly implemented with superconducting quantum devices featuring larger anharmonicity for higher coupling strengths.
arxiv pdf

Microwave-controlled generation of shaped single photons in circuit quantum electrodynamics

  1. M. Pechal,
  2. C. Eichler,
  3. S. Zeytinoglu,
  4. S. Berger,
  5. A. Wallraff,
  6. and S. Filipp
Coherent generation of single photons with waveforms of a given shape plays an important role in many protocols for quantum information exchange between distant quantum bits. Here we
create shaped microwave photons in a superconducting system consisting of a transmon circuit coupled to a transmission line resonator. Using the third level of the transmon, we exploit a second-order transition induced by a modulated microwave drive to controllably transfer an excitation to the resonator from which it is emitted into a transmission line as a travelling photon. We demonstrate the single-photon nature of the emitted field and the ability to generate photons with a controlled amplitude and phase. In contrast to similar schemes, the presented one requires only a single control line, allowing for a simple implementation with fixed-frequency qubits.
arxiv pdf