Double-lambda System Research Articles

Controlled-not gate with orbital angular momentum in a rare-earth-ion-doped solid

We experimentally demonstrate a controlled-not (CNOT) gate with vortex beams carrying orbital angular momentum (OAM) via light storage in a solid driven by electromagnetically induced transparency (EIT). We use vortex beams with different topological charges to perform EIT storage in the double lambda atomic system, the stored information is transferred into a new information channel. The topological charge of the generated signal field is determined by those of the applied fields. The OAM conservation is satisfied in this EIT storage of the double lambda system. By imposing different OAMs into the control and probe fields, we obtain a CNOT gate using EIT storage. This demonstration can be useful for better understanding and developing the OAM applications in the interactions between the OAM and the mediums.

Transfer of orbital angular momentum of light using electromagnetically induced transparency

We experimentally investigate the transfer of orbital angular momentum (OAM) of light in a solid driven by electromagnetically induced transparency (EIT). Under the condition of dynamical EIT, the OAM of the probe pulse is stored and retrieved in the experimental medium. By using a four-level double-lambda system to control the retrieval process of EIT storage, we show that OAM can be transferred from the probe field or the second control field to the newly generated signal field, which has a new spatial-frequency mode compared with the input mode. Furthermore, we use EIT-based four-wave mixing to investigate the direct OAM transfer without experiencing the storage, where we do not need to switch off and back on the control field.

Observation of Mollow Triplets with Tunable Interactions in Double Lambda Systems of Individual Hole Spins.

Although individual spins in quantum dots have been studied extensively as qubits, their investigation under strong resonant driving in the scope of accessing Mollow physics is still an open question. Here, we have grown high quality positively charged quantum dots embedded in a planar microcavity that enable enhanced light-matter interactions. Under a strong magnetic field in the Voigt configuration, individual positively charged quantum dots provide a double lambda level structure. Using a combination of above-band and resonant excitation, we observe the formation of Mollow triplets on all optical transitions. We find that when the strong resonant drive power is used to tune the Mollow-triplet lines through each other, we observe anticrossings. We also demonstrate that the interaction that gives rise to the anticrossings can be controlled in strength by tuning the polarization of the resonant laser drive. Quantum-optical modeling of our system fully captures the experimentally observed spectra and provides insight on the complicated level structure that results from the strong driving of the double lambda system.

Tuning the phase sensitivity of a double-lambda system with a static magnetic field.

We study the effect of a DC magnetic field on the phase sensitivity of a double-lambda system coupled by two laser fields, a probe and a pump. It is demonstrated that the gain and the refractive index of the probe can be controlled by either the magnetic field or the relative phase between the two laser fields. More interestingly, when the system reduces to a single-lambda system, turning on the magnetic field transforms the system from a phase-insensitive process to a phase-sensitive one. In the pulsed-probe regime, we observed switching between slow and fast light when the magnetic field or the relative phase was adjusted. Experiments using a coated 87Rb vapor cell produced results in good agreement with our numerical simulation. This work provides a novel and simple means to manipulate phase sensitive electromagnetically-induced-transparency or four-wave mixing, and could be useful for applications in quantum optics, nonlinear optics and magnetometery based on such systems.

Time-resolved detection of relative-intensity squeezed nanosecond pulses in an 87Rb vapor

We present theoretical and experimental results on the generation and detection of pulsed, relative-intensity squeezed light in a hot 87Rb vapor. The intensity noise correlations between a pulsed probe beam and its conjugate, generated through nearly degenerate four-wave mixing in a double-lambda system, are studied numerically and measured experimentally via time-resolved balanced detection. We predict and observe approximately − 1 dB of time-resolved relative-intensity squeezing with 50 ns pulses at 1 MHz repetition rate. (− 1.34 dB corrected for loss).

All-optical switching with a biexcitonic double lambda system

A double lambda four-level system could be implemented with biexcitonic transitions on GaAs quantum well. We observed that the phase dependent biexcitonic transition could be explained by interference between one-photon and three-photon transition in a double lambda four-level system. An ultralow-light switch pulse could control 80% of biexcitonic absorption, which demonstrated all-optical switching with biexcitonic double lambda system.

Thirteen pump-probe resonances of the sodiumD1line

We present the results of a pump-probe laser spectroscopic investigation of the Doppler-broadened sodium $D1$ resonance line. We find 13 resonances in the resulting spectra. These observations are well described by the numerical predictions of a four-level atomic model of the hyperfine structure of the sodium $D1$ line. We also find that many, but not all, of these features can be understood in terms of processes originating in a two-level or three-level subset of the full four-level model. The processes we observed include forward near-degenerate four-wave mixing and saturation in a two-level system, difference-frequency crossing and nondegenerate four-wave mixing in a three-level V system, electromagnetically induced transparency and optical pumping in a three-level lambda system, cross-transition resonance in a four-level double-lambda system, and conventional optical pumping. Most of these processes lead to sub-Doppler or even subnatural linewidths. The dependence of these resonances on the pump intensity and pump detuning from atomic resonance are also studied.

Efficient photon counting and single-photon generation using resonant nonlinear optics

The behavior of an atomic double lambda system in the presence of a strong off-resonant classical field and a few-photon resonant quantum field is examined. It is shown that the system possesses properties that allow a single-photon state to be distilled from a multi-photon input wave packet. In addition, the system is also capable of functioning as an efficient photodetector discriminating between one- and two-photon wave packets with arbitrarily high efficiency.

Controlled light storage in a double lambda system

It is shown theoretically that after light storing in a medium of four-level atoms it is possible to release a new pulse of a different frequency, the process being steered by another driving beam. It is also possible to store one pulse and to release two different ones, with their time separation and heights being controlled. The problem of adiabaticity of the evolution is discussed in terms of dark and bright state polaritons.

The double lambda system: a new workhorse for quantum optics?

We review the status of the double–lambda system of cavity QED and mention unexpected recent applications in which deterministic and unitary control of quantum states is exploited.