Dependence of nonlinear optical processes on intermodal correlations

Pavel Chmela

R. Tanaś

M. Schubert, B. Wilhelmi

Masahiro Takeoka, S. Sakata, Fumihiko Kannari

Summary form only given. Recent experiments have demonstrated more than 50% of photon number squeezing of optical pulses by spectral filtering method in nonlinear optical fibers. For such squeezing quantum correlations between the spectral components of the pulses play a crucial role. The intermode correlations in the squeezed pulses are mainly induced by the second-order dispersion and the third-order nonlinearity (the self-phase modulation (SPM) effect) of fibers. We numerically study the dependence of the initial pulse waveform on spectral filtering squeezing and the optimization of pulses to obtain the further squeezing. Calculations are performed by solving the quantum nonlinear Schrodinger equation (QNLSE) in the positive P representation.

Stephen R. Friberg

Kasper Alexander, Thjalfe Ulvenberg, Paweł Wyborski +10 more

Optical frequency conversion plays a key role in realizing large-scale quantum networks, including multi-qubit discrete-variable quantum computers and quantum communication links where photons serve as the fundamental qubits. However, achieving efficient conversion via nonlinear optical processes for specific target wavelengths remains a significant challenge, as precise dispersion control is essential to satisfy phase-matching conditions across specific frequency ranges. An intriguing approach to solve this challenge is leveraging the modal degree of freedom in spatially multimoded waveguides and realizing intermodal nonlinear interaction. Following this approach, we present the experimental demonstration of tunable, number-state-preserving frequency conversion of true single photons emitted from a quantum dot. The conversion is achieved in a multimode fiber and exhibits a peak internal efficiency of 85% while retaining single photon purity of 99% during conversion. Our results show that the intermodal platform presents a promising and versatile approach for overcoming phase-matching limitations in quantum frequency conversion, thus allowing the efficient interfacing of different optical quantum devices.