We demonstrate experimentally the delay of squeezed light and entanglement using Electromagnetically Induced Transparency (EIT) in a rubidium vapour cell. We perform quadrature amplitude measurements of the probe field and find no appreciable excess noise from the EIT process. From an input squeezing of 3.1 dB at low sideband frequencies, we observed the survival of 2 dB of squeezing at the EIT output. By splitting the squeezed light on a beam-splitter, we generated biased entanglement between two beams. We transmit one of the entangled beams through the EIT cell and correlate the quantum statistics of this beam with its entangled counterpart. We experimentally observed a 2 $μ$s delay of the biased entanglement and obtained a preserved degree of wavefunction inseparability of 0.71, below the unity value for separable states.
The traversal of an elliptically polarized optical field through a thermal vapour cell can give rise to a rotation of its polarization axis. This process, known as polarization self-rotation (PSR), has been suggested as a mechanism for producing squeezed light at atomic transition wavelengths. In this paper, we show results of the characterization of PSR in isotopically enhanced Rubidium-87 cells, performed in two independent laboratories. We observed that, contrary to earlier work, the presence of atomic noise in the thermal vapour overwhelms the observation of squeezing. We present a theory …
Electromagnetically induced transparency (EIT) resonances using the $5\rm{S}_{1/2}\rightarrow5\rm{P}_{3/2}\rightarrow5\rm{D}_{5/2}$ ladder-system in optically thick Rb atomic vapour are studied. We observe a strong line narrowing effect and gain at the $5\rm{S}_{1/2}\rightarrow5\rm{P}_{3/2}$ transition wavelength due to an energy-pooling assisted frequency conversion with characteristics similar to four-wave mixing. As a result it is possible to observe tunable and switchable transparency resonances with amplitude close to $100\%$ and a linewidth of 15 MHz. In addition, the large line narrowin…
The interaction of a quantized field with three-level atoms in $Λ$ configuration inside a two mode cavity is analyzed. We calculate the stationary quadrature noise spectrum of the field outside the cavity in the case where the input probe field is in a squeezed state and the atoms show electromagnetically induced transparency (EIT). If the Rabi frequencies of both dipole transitions of the atoms are different from zero, we show that the output probe field have four maxima of squeezing absorption. We show that in some cases two of these frequencies can be very close to the transition frequency …
The method for observing the high-contrast and narrow-width resonances of electromagnetically induced absorption (EIA) in the Hanle configuration under counterpropagating light waves is proposed. We theoretically analyze the absorption of a probe light wave in presence of counterpropagating one with the same frequency as the function of a static magnetic field applied along the vectors of light waves, propagating in a vapour cell. Here, as an example, we study a "dark" type of atomic dipole transition Fg=1-->Fe=1 in D1 line of 87Rb, where usually the electromagnetically induced transparency (E…
We report on the use of parametric excitation to coherently manipulate the collective spin state of an atomic vapour at room temperature. Signatures of the parametric excitation are detected in the ground-state spin evolution. These include the excitation spectrum of the atomic coherences, which contains resonances at frequencies characteristic of the parametric process. The amplitudes of the signal quadratures show amplification and attenuation, and their noise distribution is characterized by a strong asymmetry, similarly to those observed in mechanical oscillators. The parametric excitation…
We observe electromagnetically induced transparency (EIT) on the 5s to 5p transition in a room temperature rubidium vapour cell by coupling the 5p state to a Rydberg state (ns or nd with n=26 to 124). We demonstrate that the narrow line-width of the EIT resonance (2 MHz) allows precise measurement of the d state fine structure splitting, and together with the sensitivity of the Rydberg state to electric fields, we are able to detect transient electric fields produced by the dynamics of charges within the cell. Coherent coupling of Rydberg states via EIT could also be used for cross-phase modul…
We experimentally and theoretically analyze the transmission of continuous-wave and pulsed squeezed vacuum through rubidium vapor under the conditions of electromagnetically induced transparency. Frequency- and time-domain homodyne tomography is used to measure the quadrature noise and reconstruct the quantum states of the transmitted light. A simple theoretical model explains the spectrum and degradation of the transmitted squeezing with high precision.
We consider the quantum effect of slow light dark soliton (SLDS) in a cold atomic gas with defocuing Kerr nonlinearity via electromagnetically induced transparency (EIT). We calculate the quantum fluctuations of the SLDS by solving the relevant non-Hermitian eigenvalue problem describing the quantum fluctuations, and find that only one zero mode is allowed. This is different from the quantum fluctuations of bright solitons, where two independent zero modes occur. We rigorously prove that the eigenmodes, which consist of continuous modes and the zero mode, are bi-orthogonal and constitute a com…
We show that a quasi-perfect quantum state transfer between an atomic ensemble and fields in an optical cavity can be achieved in Electromagnetically Induced Transparency (EIT). A squeezed vacuum field state can be mapped onto the long-lived atomic spin associated to the ground state sublevels of the Lambda-type atoms considered. The EIT on-resonance situation show interesting similarities with the Raman off-resonant configuration. We then show how to transfer the atomic squeezing back to the field exiting the cavity, thus realizing a quantum memory-type operation.
We analyse a novel squeezing and entangling mechanism which is due to correlated Stokes and anti-Stokes photon forward scattering in a multi-level atom vapour. Following the proposal we present an experimental demonstration of 3.5 dB pulsed frequency nondegenerate squeezed (quadrature entangled) state of light using room temperature caesium vapour. The source is very robust and requires only a few milliwatts of laser power. The squeezed state is generated in the same spatial mode as the local oscillator and in a single temporal mode. The two entangled modes are separated by twice the Zeeman fr…
We observed squeezed vacuum light at 795 nm in 87Rb vapor via resonant polarization self-rotation, and report noise sidebands suppression of ~1 dB below shot noise level spanning from acoustic (30 kHz) to MHz frequencies. This is the first demonstration of sub-MHz quadrature vacuum squeezing in atomic systems. The spectral range of observed squeezing matches well typical bandwidths of electromagnetically induced transparency (EIT) resonances, making this simple technique for generation of optical fields with non-classical statistics at atomic transitions wavelengths attractive for EIT-based qu…
We investigate, theoretically and experimentally, the transmission of light through a thermal vapour of three-level ladder-type atoms, in the presence of 2 counter-propagating control fields. A simple theoretical model predicts the presence of electromagnetically induced absorption (EIA) in this pure three-level system when the control field is resonant. Experimentally, we use $^{87}$Rb in a large magnetic field of 0.62~T to reach the hyperfine Paschen-Back regime and realise a non-degenerate three-level system. Experimental observations verify the predictions over a wide range of detunings.
Quantum entanglement is an essential ingredient for the absolute security of quantum communication. Generation of continuous-variable entanglement or two-mode squeezing between light fields based on the effect of electromagnetically induced transparency (EIT) has been systematically investigated in this work. Here, we propose a new scheme to enhance the degree of entanglement between probe and coupling fields of coherent-state light by introducing a two-photon detuning in the EIT system. This proposed scheme is more efficient than the conventional one, utilizing the dephasing rate of ground-st…
An inconsistency was found in the equations used to calculate the variance of the quadrature fluctuations of a field propagating through a medium demonstrating electromagnetically induced transparency (EIT). The decoherence term used in our original paper introduces inconsistency under weak probe approximation. In this erratum we give the Bloch equations with the correct dephasing terms. The conclusions of the original paper remain the same. Both entanglement and squeezing can be delayed and preserved using EIT without adding noise when the decoherence rate is small.
We study the multipartite correlations of the multi-atom dark states, which are characterized by the atomic squeezing beyond the pairwise entanglement. It is shown that, in the photon storage process with atomic ensemble via electromagnetically induced transparency (EIT) mechanism, the atomic squeezing and the pairwise entanglement can be created by adiabatically manipulating the Rabi frequency of the classical light field on the atomic ensemble. We also consider the sudden death for the atomic squeezing and the pairwise entanglement under various decoherence channels. An optimal time for gene…
Invisibility cloaking imposes strict conditions on the refractive index profiles of cloaking media that must be satisfied to successfully hide an object. The first experimental demonstrations of cloaking used artificial metamaterials to respond to this challenge. In this work we show how a much simpler technique of electromagnetically induced transparency can be used to achieve a partial, {\it carpet} cloaking at optical frequencies in atomic vapours or solids. To generate a desired combination of low absorption with strong modifications of the refractive index, we use chiral media with an ind…
We present direct measurements of the hyperfine splitting of Rydberg states in rubidium 87 using Electromagnetically Induced Transparency (EIT) spectroscopy in a room-temperature vapour cell. With this method, and in spite of Doppler-broadening, line-widths of 3.7 MHz FWHM, i.e. significantly below the intermediate state natural linewidth are reached. This allows resolving hyperfine splittings for Rydberg s-states with n=20...24. With this method we are able to determine Rydberg state hyperfine splittings with an accuracy of approximately 100 kHz. Ultimately our method allows accuracies of ord…
We investigate the quantum squeezing of slow-light solitons generated in a $Λ$-shaped three-level atomic system working under condition of electromagnetically induced transparency (EIT). We show that due to the giant Kerr nonlinearity contributed from the EIT effect, significant quantum squeezing of the slow-light soliton can be realized within a short propagation distance. The results reported here are helpful for understanding the quantum property of slow-light solitons and for realizing light squeezing via EIT in cold atomic gases experimentally.
We study the effects of frequency-dependent squeeze amplitude attenuation and squeeze angle rotation by electromagnetically induced transparency (EIT) on gravitational wave (GW) interferometers. We propose the use of low-pass, band-pass, and high-pass EIT filters, an S-shaped EIT filter, and an intra-cavity EIT filter to generate frequency-dependent squeezing for injection into the antisymmetric port of GW interferometers. We find that the EIT filters have several advantages over the previous filter designs with regard to optical losses, compactness, and the tunability of the filter linewidth.
We examine the interaction of a weak probe with $N$ atoms in a lambda-level configuration under the conditions of electromagnetically induced transparency (EIT). In contrast to previous works on EIT, we calculate the output state of the resultant slowly propagating light field while taking into account the effects of ground state dephasing and atomic noise for a more realistic model. In particular, we propose two experiments using slow light with a nonclassical probe field and show that two properties of the probe, entanglement and squeezing, characterizing the quantum state of the probe field…
As one of the most influential experiments on the development of modern macroscopic theory from Newtonian mechanics to Einstein's special theory of relativity, the phenomenon of light dragging in a moving medium has been discussed and observed extensively in different types of systems. To have a significant dragging effect, the long duration of light travelling in the medium is preferred. Here we demonstrate a light-dragging experiment in an electromagnetically induced transparent cold atomic ensemble and enhance the dragging effect by at least three orders of magnitude compared with the previ…
We produce a 600-ns pulse of 1.86-dB squeezed vacuum at 795 nm in an optical parametric amplifier and store it in a rubidium vapor cell for 1 us using electromagnetically induced transparency. The recovered pulse, analyzed using time-domain homodyne tomography, exhibits up to 0.21+-0.04 dB of squeezing. We identify the factors leading to the degradation of squeezing and investigate the phase evolution of the atomic coherence during the storage interval.
We report on the generation of more than 5 dB of vacuum squeezed light at the Rubidium D1 line (795 nm) using periodically poled KTiOPO$_{4}$ (PPKTP) in an optical parametric oscillator. We demonstrate squeezing at low sideband frequencies, making this source of non-classical light compatible with bandwidth limited atom optics experiments. When PPKTP is operated as a parametric amplifier, we show a noise reduction of 4 dB stably locked within the 150 kHz-500 kHz frequency range. This matches the bandwidth of Electromagnetically Induced Transparency (EIT) in Rubidium hot vapour cells under the …
With our all-atomic squeezing and filtering setup, we demonstrate control over the noise amplitudes and manipulation of the frequency-dependent squeezing angle of a squeezed vacuum quantum state by passing it through an atomic medium with electromagnetically induced transparency (EIT). We generate low sideband frequency squeezed vacuum using the polarization self-rotation effect in a hot Rb vapor cell, and input it into a second atomic vapor subject to EIT conditions. We use the frequency-dependent absorption of the EIT window to demonstrate an example of squeeze amplitude attenuation and sque…
We demonstrate the non-dispersive deflection of an optical beam in a Stern-Gerlach magnetic field. An optical pulse is initially stored as a spin-wave coherence in thermal rubidium vapour. An inhomogeneous magnetic field imprints a phase gradient onto the spin wave, which upon reacceleration of the optical pulse leads to an angular deflection of the retrieved beam. We show that the obtained beam deflection is non-dispersive, i.e. its magnitude is independent of the incident optical frequency. Compared to a Stern-Gerlach experiment carried out with propagating light under the conditions of elec…
We study the effect of a control beam on a Lambda electromagnetically induced transparency (EIT) system in 87Rb. The control beam couples one ground state to another excited state forming a four level N-system. Phase coherent beams to drive the N-system are produced using a double injection scheme. We show that the control beam can be used to Stark shift or split the EIT resonance. Finally, we show that the when the control beam is on-resonance one observes a Doppler-free and sub-natural absorptive resonance with a width of order 100 kHz. Crucially, this narrow absorptive resonance only occurs…
