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, the 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 linked efficiently because of the orders-of-magnitude mismatch in the timescales or, correspondingly, spectral linewidths. Here we develop a large-aperture time lens using wide-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. This 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. To bridge the ultrafast and slow classes of quantum-information-processing systems, a Fresnel time lens is developed by using a wideband electro-optic phase modulator combined with a dispersion element. The single-photon spectral bandwidth is compressed from picosecond to nanosecond timescales.
Atoms are ideal quantum sensors and quantum light emitters. Interfacing atoms with nanophotonic devices promises nanoscale sensing and quantum optical functionalities. But precise optical control of atomic states in these devices is challenged by the spatially varying light-atom coupling strength, which is generic to nanophotonic devices. We demonstrate numerically that despite the inhomogeneity, composite picosecond optical pulses with optimally tailored phases are able to evanescently control the atomic electric dipole transitions nearly perfectly, with fidelity $f>99\mathrm{%}$ across volumes large enough for, e.g., controlling cold atoms confined in near-field optical lattices. Our proposal is followed by a proof-of-principle demonstration with a
85Rb-vapor--optical-nanofiber interface, where the excitation by an
N=3 sequence of guided picosecond
D1 control pulses reduces the absorption of a coguided nanosecond
D2 probe pulse by up to approximately $70\mathrm{%}$. The close-to-ideal performance is corroborated by comparing the absorption data across the parameter space with first-principles modeling of the mesoscopic atomic vapor response. Extension of the composite technique to $N\ensuremath{\ge}\phantom{\rule{0.2em}{0ex}}5$ appears highly feasible to support arbitrary local control of atomic dipoles with exquisite precision. This unprecedented ability would allow error-resilient atomic spectroscopy and open up a variety of research opportunities in nanophotonic quantum optics.
Atoms are ideal quantum sensors and quantum light emitters. Interfacing atoms with nanophotonic devices promises novel nanoscale sensing and quantum optical functionalities. But precise optical control of atomic states in these devices is challenged by the spatially varying light-atom coupling strength, generic to nanophotonic. We demonstrate numerically that despite the inhomogenuity, composite picosecond optical pulses with optimally tailored phases are able to evanescently control the atomic electric dipole transitions nearly perfectly, with
f>99% fidelity across large enough volumes for {\it e.g.} controlling cold atoms confined in near-field optical lattices. Our proposal is followed by a proof-of-principle demonstration with a
85Rb vapor -- optical nanofiber interface, where the excitation by an
N=3 sequence of guided picosecond D1 control reduces the absorption of a co-guided nanosecond D2 probe by up to
∼70%. The close-to-ideal performance is corroborated by comparing the absorption data across the parameter space with first-principle modeling of the mesoscopic atomic vapor response. Extension of the composite technique to
N≥5 appears highly feasible to support arbitrary local control of atomic dipoles with exquisite precision. This unprecedented ability would allow error-resilient atomic spectroscopy and open up novel nonlinear quantum optical research with atom-nanophotonic interfaces.