  Light is a key information carrier, enabling worldwide high-speed data
transmission through a telecommunication fibre network. This
information-carrying capacity can be extended to transmitting quantum
information (QI) by encoding it in single photons -- flying qubits. However,
various QI-processing platforms operate at vastly different timescales.
QI-processing units in atomic media, operating within nanosecond to microsecond
timescales, and high-speed quantum communication, at picosecond timescales,
cannot be efficiently linked due to orders of magnitude mismatch in the
timescales or, correspondingly, spectral linewidths. In this work, we develop a
large-aperture time lens using complex high-bandwidth electro-optic phase
modulation to bridge this gap. We demonstrate coherent, deterministic spectral
bandwidth compression of quantum light pulses by more than two orders of
magnitude with high efficiency. It will facilitate large-scale hybrid
QI-processing by linking the ultrafast and quasi-continuous-wave experimental
platforms, which until now, to a large extent, have been developing
independently.
