Quantum transduction is the manipulation coherent quantum states at the boundaries of quantum systems, and it lies at the heart of engineering these "systems" into networks, sensors or computers. Coherent transduction of quantum states between microwave and optical frequencies is an essential component of many emerging quantum information science (QIS) applications, as it provides an effective way for linking the classical and quantum world or transporting information on macroscopic scales. The performance of quantum systems that require microwave-optical transduction in practical applications will be determined by the achievable data rates and fidelity in transferring quantum information between these two extreme wavelengths. Unfortunately, direct transduction from microwave to optical frequencies is inherently dissipative, leading to thermal losses which limit the achievable performance of microwave quantum sensors and circuits operating at millikelvin (mK) temperatures. To overcome this limitation, a fundamentally new approach is needed.
Rather than direct transduction to optical frequencies, we are utilizing the mm-wave regime as an intermediate state in a two-step transduction scheme. Our "quantum bus" would perform the microwave to mm-wave transduction with a superconducting resonator at mK temperatures before transporting the photon and its quantum information to higher temperatures and potentially being up-converted into the optical range. Converting to mm-wave frequencies can be achieved with much lower dissipation, and even at these intermediate photon energies coherence can be maintained at elevated temperatures. While optical links are the best solution for long-range massively-parallel networks, low-loss mm-wave photonics would also allow preservation of quantum information at room temperature for a simpler network at laboratory scales.
Emilio Nanni received his Ph.D. in Electrical Engineering from MIT in 2013. He joined SLAC National Accelerator Laboratory and Stanford University in 2015; his research is focused applied electromagnetics; high power, high-frequency vacuum electron devices; optical THz amplifiers; electron-beam dynamics; and advanced accelerator concepts. He recently joined the faculty of Stanford as an Assistant Professor of Photon Science and of Particle Physics and Astrophysics. Prior to his time at Stanford, he completed his postdoc at MIT with a joint appointment in the Nuclear Reactor Lab and the Research Laboratory for Electronics where he participated in the demonstration of the first acceleration of electrons with optically generated THz pulses. For his PhD he worked on high-frequency high-power THz sources and the development of Nuclear Magnetic Resonance spectrometers using Dynamic Nuclear Polarization. His thesis was on the first photonic-band-gap gyrotron travelling wave amplifier which demonstrated record power and gain levels in the THz frequency band.