10 research outputs found
Observation of squeezed light from one atom excited with two photons
Single quantum emitters like atoms are well-known as non-classical light
sources which can produce photons one by one at given times, with reduced
intensity noise. However, the light field emitted by a single atom can exhibit
much richer dynamics. A prominent example is the predicted ability for a single
atom to produce quadrature-squeezed light, with sub-shot-noise amplitude or
phase fluctuations. It has long been foreseen, though, that such squeezing
would be "at least an order of magnitude more difficult" to observe than the
emission of single photons. Squeezed beams have been generated using
macroscopic and mesoscopic media down to a few tens of atoms, but despite
experimental efforts, single-atom squeezing has so far escaped observation.
Here we generate squeezed light with a single atom in a high-finesse optical
resonator. The strong coupling of the atom to the cavity field induces a
genuine quantum mechanical nonlinearity, several orders of magnitude larger
than for usual macroscopic media. This produces observable quadrature squeezing
with an excitation beam containing on average only two photons per system
lifetime. In sharp contrast to the emission of single photons, the squeezed
light stems from the quantum coherence of photon pairs emitted from the system.
The ability of a single atom to induce strong coherent interactions between
propagating photons opens up new perspectives for photonic quantum logic with
single emittersComment: Main paper (4 pages, 3 figures) + Supplementary information (5 pages,
2 figures). Revised versio
Efficient coupling of photons to a single molecule and the observation of its resonance fluorescence
Single dye molecules at cryogenic temperatures display many spectroscopic
phenomena known from free atoms and are thus promising candidates for
fundamental quantum optical studies. However, the existing techniques for the
detection of single molecules have either sacrificed the information on the
coherence of the excited state or have been inefficient. Here we show that
these problems can be addressed by focusing the excitation light near to the
absorption cross section of a molecule. Our detection scheme allows us to
explore resonance fluorescence over 9 orders of magnitude of excitation
intensity and to separate its coherent and incoherent parts. In the strong
excitation regime, we demonstrate the first observation of the Mollow triplet
from a single solid-state emitter. Under weak excitation we report the
detection of a single molecule with an incident power as faint as 150 attoWatt,
paving the way for studying nonlinear effects with only a few photons.Comment: 6 figure
Quadrature squeezed photons from a two-level system.
Resonance fluorescence arises from the interaction of an optical field with a two-level system, and has played a fundamental role in the development of quantum optics and its applications. Despite its conceptual simplicity, it entails a wide range of intriguing phenomena, such as the Mollow-triplet emission spectrum, photon antibunching and coherent photon emission. One fundamental aspect of resonance fluorescence--squeezing in the form of reduced quantum fluctuations in the single photon stream from an atom in free space--was predicted more than 30 years ago. However, the requirement to operate in the weak excitation regime, together with the combination of modest oscillator strength of atoms and low collection efficiencies, has continued to necessitate stringent experimental conditions for the observation of squeezing with atoms. Attempts to circumvent these issues had to sacrifice antibunching, owing to either stimulated forward scattering from atomic ensembles or multi-photon transitions inside optical cavities. Here, we use an artificial atom with a large optical dipole enabling 100-fold improvement of the photon detection rate over the natural atom counterpart and reach the necessary conditions for the observation of quadrature squeezing in single resonance-fluorescence photons. By implementing phase-dependent homodyne intensity-correlation detection, we demonstrate that the electric field quadrature variance of resonance fluorescence is three per cent below the fundamental limit set by vacuum fluctuations, while the photon statistics remain antibunched. The presence of squeezing and antibunching simultaneously is a fully non-classical outcome of the wave-particle duality of photons.We acknowledge financial support from the University of Cambridge, the European Research Council ERC Consolidator Grant Agreement No. 617985 and the EU-FP7 Marie Curie Initial Training Network S3NANO. C.M. acknowledges Clare College Cambridge for financial support through a Junior Research Fellowship.This is the author accepted manuscript. The final version is available from Nature Publishing Group via http://dx.doi.org/10.1038/nature1486
Phase-locked indistinguishable photons with synthesized waveforms from a solid-state source
Resonance fluorescence in the Heitler regime provides access to single
photons with coherence well beyond the Fourier transform limit of the
transition, and holds the promise to circumvent environment-induced dephasing
common to all solid-state systems. Here we demonstrate that the coherently
generated single photons from a single self-assembled InAs quantum dot display
mutual coherence with the excitation laser on a timescale exceeding 3 seconds.
Exploiting this degree of mutual coherence we synthesize near-arbitrary
coherent photon waveforms by shaping the excitation laser field. In contrast to
post-emission filtering, our technique avoids both photon loss and degradation
of the single photon nature for all synthesized waveforms. By engineering
pulsed waveforms of single photons, we further demonstrate that separate
photons generated coherently by the same laser field are fundamentally
indistinguishable, lending themselves to creation of distant entanglement
through quantum interference.Comment: Additional data and analysis in PDF format is available for download
at the publications section of our website:
http://www.amop.phy.cam.ac.uk/amop-ma