I am a Postdoctoral Scholar in the Department of Electrical Engineering and at the Institute of Quantum Information and Matter (IQIM) at Caltech. I obtained my Ph.D. from Cornell University in 2020 and my bachelors from the Indian Institute of Technology Bombay.
Contact
cjoshi at caltech dot edu
Research Interests
I am a quantum physicist interested in building scalable hardware for the next generation of quantum computers and networks. Currently, I work with superconducting circuits and have extensive experience in microwave device design, EM simulations, nanofabrication, and cryogenic measurements. During my Ph.D., I worked on quantum nonlinear photonics, developing deterministic single-photon sources and tools for time-frequency manipulation of light in the quantum regime. Below, you can find publications from some of my projects.
Curriculum Vitae
Publications
See Google Scholar for a list of my publications.
Current research projects
Chiral light-matter interface with superconducting qubits
Chiral light-matter interactions can enable applications such as the realization of all-to-all connectivity between remote nodes for quantum networks and error-correction schemes, quantum state transfer immune to thermal noise, and the generation of many-body entangled states. In recent work (arXiv:2212.11400), we realized a chiral interface in the microwave domain using a transmon qubit operating in the giant atom regime, with the atom waveguide interaction mediated by time-modulated couplings. This approach does not require ferromagnetic materials and may provide a low-loss, chip-scale alternative for realizing non-reciprocal interactions in the microwave domain.
Kinetic-inductance devices of millimeter-wave applications
KI nonlinearity of disordered superconductors can potentially be used for engineering nonlinear quantum elements that are resilient to quasiparticle noise in the mm-wave (100 GHz) spectrum and at elevated operating temperatures. In recent work (PhysRevApplied.18.064088), we developed kinetic-inductance (KI) resonators engineered to have a strongly nonlinear response, with the Kerr shift per photon comparable to the dissipation rate. The resonators use a nanowire geometry with a small volume V ≃ 10 − 4μm3 to amplify the current zero-point fluctuations and the resulting nonlinear response. With this extreme resonator geometry, we measure a Kerr shift per photon of 123 kHz and a nonlinearity-to-loss ratio of 21% in the best devices. With improved fabrication and design, our resonators can approach the regime of strong quantum nonlinearity in devices operating at higher frequencies, with implications for the frequency conversion of microwave to mm-wave photons, for developing quantum links operating at 1K, and for engineering non-classical states of radiation in the mm-wave spectrum.