Electro-Optic Modulation of Single Photons

Abstract

We use the Stokes photon of a biphoton pair to set the time origin for electro-optic modulation of the wave function of the anti-Stokes photon thereby allowing arbitrary phase and amplitude modulation. We demonstrate conditional single-photon wave functions composed of several pulses, or instead, having gaussian or exponential shapes.PACS numbers: 42.50. Gy, 32.80.Qk, 42.50.Ex, 42.65.Lm This letter demonstrates how single photons may be modulated so as to produce photon wave functions whose amplitude and phase are functions of time. The essential feature of this work is the use of one photon of a biphoton pair that is generated by spontaneous parametric down-conversion to establish the time origin for the modulation of the second photon. This is done by using electromagnetically induced transparency and slow light to produce time-energy entangled biphotons with pulse lengths of several hundred ns, and therefore, very long as compared to the temporal resolution of single photon counting modules (about 40 ps). Once the time origin is established, the photon waveform may be modulated in the same manner as one modulates a classical pulse of light. For example, the single-photon waveform may be phase, frequency, amplitude, or even digitally modulated, with the maximum modulation frequency limited by the resolution of the detection of the first photon.As shown in Fig. 1, we use cw pump and coupling lasers to generate time-energy entangled pairs of Stokes and anti-Stokes photons that propagate in opposite directions and are collected in single mode fibers. The detection of a Stokes photon at D 1 sets the time origin for firing the function generator that drives the electro-optic modulator (EOM) that modulates the wave function of the anti-Stokes photon. This latter photon is incident on the beam splitter where it is detected by D 2 or D 3 . As shown in the following, we generate single photons whose modulated waveform is two rectangular pulses, is Gaussian or is a time reversed exponential.The method demonstrated in this letter might be used to optimally load a single photon into an optical cavity [1], or instead, to study the transient response of atoms to different single photon waveforms. In the context of light-matter interfaces, it may improve the efficiency of storage and retrieval of single photons in atomic ensembles [2]. For quantum information applications, both amplitude and phase modulators could be used to allow full control over the single photon waveforms. For example, one could a construct a single photon waveform that is a train of identical pulses with information encoded into the relative phase difference between consecutive pulses [3].The generation of single photons with controlled wave- forms has been demonstrated earlier by using the techniques of cavity-QED, i.e., by coupling a single trapped ion to a high Q cavity and using an acousto-optic modulator to shape a pumping laser that is tuned close to the resonant transition [4]. In related work Rempe and colleagues use a single Rb atom, again i...

Temporal Purity and Quantum Interference of Single Photons from Two Independent Cold Atomic Ensembles

“…Different from the external spectral filtering in the SPDC scheme, the EIT effect governs not only the transmission of the photons but mainly the phase matching condition of the FWM process. The phase matching condition, therefore, is dependent on the atomic ensemble and the coupling field and can be manipulated temporally much more easily [38][39][40][41][42]. In this Letter, we show that the heralded single photon with a coherence time of 100 ns directly heralded from time-frequency entangled biphotons generated from cold atom clouds is in a temporally pure quantum state.…”

Optical Precursor of a Single Photon

“…In this work, we successfully separate these precursors from the main wave packet by passing one of the paired photons through an EIT slow-light system. Moreover, with heralded single photons whose waveform are shaped by an electro-optic modulator(EOM) [24], we can generate single-photon precursors. Our result suggests that the causality holds for a single photon.…”

Narrowband Biphotons: Generation, Manipulation, and Applications

“…The long coherence time of these narrow-band biphotons allows us to not only directly resolve their temporal waveform with existing commercial single photon detectors (with a typical resolution of 1 ns) but also manipulate their quantum waveform with external phase-amplitude modulators [53,54]. In addition, compared with SPDC using a single pump laser, there are more freedoms to manipulate the the biphoton generation in SFWM with two driving lasers.…”

“…As shown in Fig. 12, The heralded single photons can be modulated into two rectangular pulses, Gaussian or time reversed exponential [53]. The importance of the electro-optic method is its speed and ability to modulate phase as well as amplitude.…”