Coherent population trapping resonances in the presence of the frequency-phase noises of an exciting field (original) (raw)
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Optically controlled locking of the nuclear field via coherent dark-state spectroscopy
Nature, 2009
A single electron or hole spin trapped inside a semiconductor quantum dot forms the foundation for many proposed quantum logic devices 1-6 . In group III-V materials, the resonance and coherence between two ground states of the single spin are inevitably affected by the lattice nuclear spins through the hyperfine interaction 7-9 , while the dynamics of the single spin also influence the nuclear environment 10-15 . Recent efforts have been made to protect the coherence of spins in quantum dots by suppressing the nuclear spin fluctuations. However, coherent control of a single spin in a single dot with simultaneous suppression of the nuclear fluctuations has yet to be achieved. Here we report the suppression of nuclear field fluctuations in a singly charged quantum dot to well below the thermal value, as shown by an enhancement of the single electron spin dephasing time T 2 *, which we measure using coherent dark-state spectroscopy. The suppression of nuclear fluctuations is found to result from a hole-spin assisted dynamic nuclear spin polarization feedback process, where the stable value of the nuclear field is determined only by the laser frequencies at fixed laser powers. This nuclear field locking is further demonstrated in a three-laser measurement, indicating a possible enhancement of the electron spin T 2 * by a factor of several hundred. This is a simple and powerful method of enhancing the electron spin coherence time without use of 'spin echo'-type techniques 8,12 . We expect that our results will enable the reproducible preparation of the nuclear spin environment for repetitive control and measurement of a single spin with minimal statistical broadening.
Frequency-modulation spectroscopy of coherent dark resonances of multilevel atoms in magnetic field
Proceedings of SPIE, 2010
The results of frequency-modulation (FM) spectroscopy of coherent dark resonances from the Zeeman sublevels of the transition F = 2 ↔ F = 1 of D 1 line in absorption of 87 Rb atoms are presented and discussed in detail. By contrast with the conventional spectroscopy of coherent dark resonances employing two laser beams, relative frequency of which can be varied, these data has been obtained with the help of a single frequency-modulated laser field. Variation of the modulation frequency plays then a similar role as the variation of the relative frequency in conventional spectroscopy. Experimental data are fit to the theoretical calculations, which are based on the theory of FM spectroscopy of coherent dark resonances recently developed by us. Feasibility of using such experimental technique for accurate measurements of magnetic fields is also discussed.
Competition of dark states: Optical resonances with anomalous magnetic field dependence
A different type of optical resonance has been observed in Doppler-free saturated absorption spectroscopy when the pump beam has elliptical polarization slightly deviating from the ϩ and the probe has Ϫ polarization. An interpretation in terms of competition between two trap states and a dressed-atom model is presented. The observed extreme sensitivity of the resonance frequency to the external magnetic field is attributed to the ''scissors effect'' of the dressed states' crossing point.
Optical switching by controlling the double-dark resonances in a N-tripod five-level atom
Optics Communications, 2008
We have investigated the optical switching in a five-level atom in a novel configuration of electromagnetically induced transparency. This N-tripod type level scheme combines the attractive features of cross-phase modulation appearing in N-type atoms with the ability to slow light pulses associated with tripod atoms. The addition of a new driving field to the usual tripod configuration allows to control the double-dark resonances which appear in the four-level tripod system and thus enables to manipulate the probe absorption and dispersion properties. We have studied the temporal dynamics of two pulses, a probe pulse and a switch propagating pulse through the sample. In the presence of the switching field, a deep in the absorption at resonance due to one-photon electromagnetically induced transparency appears and the atomic system is transparent to the probe field, which propagates at a very small group velocity. By tuning the fields, one of the usual double-dark resonances appearing in tripod system can be controlled (Stark-shifted) and the medium, which is transparent in the absence of the control field, will become highly absorptive. The linear and cross-phase modulation susceptibilities have been calculated and we predict the possibility to realize two-photon switching and giant cross-phase modulation. Finally we address the question about the generation of an entangled coherent state and we show that the giant cross-phase modulation provided by this N-tripod atomic system can be used for realizing polarization quantum phase gates.
Quantum control of an optically dense atomic medium: Pulse shaping in a V-type three-level system
2020
In this paper, we suggest a straightforward technique to control the atomic population inversion in a three-level dense medium based on the pulse shaping with a phase-jump. A strong stokes field and two weak probe fields excite the atomic medium via the V-type configuration. First, we reveal that the atomic population inversion is accomplished under a shaped pulse. Second, we show that this is significantly improved by including a phase-jump in the pulse profile. Finally, we suggest a typical combined shape and phase in order to control the dynamics of the atomic population inversion. Introduction The interaction of quantum systems with light has drawn considerable interest due to their significant impact in several fields of Physics [1]. In fact, these interactions form the basis of a wide range of applied technology, such as laser beams, diodes [2], atomic clocks[3,4], nano-lasers [5], single photon transistors [6,7], nanophotonics [8] and all optical modulators and sensors [9]. Furthermore, light-matter interaction based on quantum coherence lays the foundation for studies in quantum optics[10-14]. In fact, coherent control of light is considered as one of the main sources of quantum interference and aims to enhance non-linear optical processes in spectroscopy and microscopy [15,16]. In the field of atomic and molecular optics, rapid progress has emerged thanks to the coherent control of light with pulse shaping [17-19]. In fact, pulse shaping methods allow the generation of designable optical wave-forms made according to user specifications. Based on pulse shaping, single beams as well as coherent anti-Stokes Raman scattering techniques called (CARS) allow chemically selective non-linear spec-troscopy [20]. This has given rise to many new directions, such as quantum computing and data communications with terabit/s [21]. The target of pulse shaping is the control of amplitude, frequency, and phase. One pertinent example is the Laser pulse shaping via the chirp frequency technique, used in [22] to control the excitation probability of a two-level system. In that study, the dependence of the population of the upper energy level on the chirp was investigated for different radiation intensities and pulse durations. Nonetheless, pulse shaping and developments in femto-second pulse techniques[19] have a significant effect on the advancement of many fields such as nuclear magnetic resonance (NMR)[23-25], spectroscopy[26], non-linear fiber optics [27-29], and high-energy physics[30,17,31-33]. Additionally, pulse shaping techniques provide a significant insight into an interdisciplinary approach leading to important results in biology [34,35]. In this work, we consider a classical multi-level atom, where we apply a strong light pulse and two weak probe lights to excite Rubidium atoms in a V-type configuration. We show that, by manipulating the shape of the stokes field, we realize the atomic population inversion. In addition, we enhance it by applying a phase-jump to the control field. This paper is organized as follows: In the first section, we present the model. In the second section, we analyse and describe our system in terms of the density matrix formalism, then we present the results in the third section followed by concluding remarks. Model In this model, a typical three-level atomic medium with a V-type configuration is considered (Fig. 1). The different levels denoted by (m, l) where (m, l = 1, 3) are coupled to the corresponding (m, l) fields as follows: the field E c with a Rabi frequency Ω c drives the level |2〉 to the
Physical Review A, 2019
Frequency-resolved quantum correlation of resonance fluorescence is investigated in a two-atom radiating system. In this quantum radiating system, only one atom is driven by a laser field, and the spontaneous transition of the undriven atom resonates with one of the Rabi sidebands of the driven atom. A single-mode empty cavity is applied to serve as a Lorentzian filter to output the superbunched fluorescent photon pairs when its frequency is tuned to halfway between the central peak and one of the side peaks. In the case of large filter width, twophoton correlation signal and its physical correspondence can be bridged analytically in our approach. It reveals that this superbunching effect turns out to be the constructive quantum interference between a pair of coupled two-photon cascaded transitions. Ulteriorly, it is the consequence of the modulations of the unfiltered dressedstate transition amplitudes by the filter. Our analytical formalism also shows that, although the dipole-dipole interaction is usually weak, the interatomic coherence caused by this weak perturbation can also play a crucial role in breaking through the superbunching limit obtained from a single two-level atom in the same parameter regime. In addition to being a treasurable quantum pump to probe into the target quantum system, it is also found in our investigation that this superbunched fluorescence can serve as a promising quantum response in detecting this weak perturbation in the interior of the quantum source. A general case is also considered when the two-atom radiating system is monitored by two filter-detector monitoring systems. It is found that this filtered strong quantum correlation can be maintained even though the two photons are spatially separated.