Bandwidth manipulation of quantum light by an electro-optic time lens

By employing electro-optic phase modulation, a time-lens imaging system is demonstrated for single-photon pulses. Such a system achieves wavelength-preserving sixfold bandwidth compression of single-photon states in the near-infrared spectral region. The ability to manipulate the spectral-temporal waveform of optical pulses has enabled a wide range of applications from ultrafast spectroscopy 1 to high-speed communications 2 . Extending these concepts to quantum light has the potential to enable breakthroughs in optical quantum science and technology 3 , 4 , 5 . However, filtering and amplifying often employed in classical pulse shaping techniques are incompatible with non-classical light. Controlling the pulsed mode structure of quantum light requires efficient means to achieve deterministic, unitary manipulation that preserves fragile quantum coherences. Here, we demonstrate an electro-optic method for modifying the spectrum of non-classical light by employing a time lens 6 , 7 , 8 . In particular, we show highly efficient, wavelength-preserving, sixfold compression of single-photon spectral intensity bandwidth, enabling over a twofold increase of single-photon flux into a spectrally narrowband absorber. These results pave the way towards spectral-temporal photonic quantum information processing and facilitate interfacing of different physical platforms 9 , 10 , 11 where quantum information can be stored 12 or manipulated 13 .