Rabi Frequency Research Articles

Floquet geometric entangling gates in ground-state manifolds of Rydberg atoms

We propose new applications of Floquet theory in Rydberg atoms for constructing quantum entangling gates in atomic ground-state manifolds. By dynamically periodically modulating the Rabi frequencies of transitions between ground and Rydberg states of atoms, error-resilient two-qubit entangling gates can be implemented in the regime of Rydberg blockade. According to different degrees of Floquet theory utilization, the fidelity of the resulting controlled gates surpasses that of the original reference, and it exhibits high robustness against Rabi error in two qubits and detuning error in the control qubit. Our method only uses encoding in the ground states, and compared to the original scheme using Rydberg state for encoding, it is less susceptible to environmental interference, making it more practical to implement. Therefore, our approach may have broader applications or potential for further expansion of geometric quantum computation with neutral atoms.

Robust discriminator of chiral molecules via a topological invariant.

We propose a scheme for chirality discrimination via a topological invariant. The physical model is based on a three-level subspace of a molecule. By modulating the components of the control field with proper frequencies, two different two-level effective Hamiltonians are derived for the left-handed and the right-handed molecules. We parameterize the effective Hamiltonians with two angles and demonstrate that a topological quantum phase transition can be induced by tuning the effective Rabi frequency if the molecule is right-handed. This phenomenon provides a method to discriminate the chirality of the molecule by measuring a topological invariant, i.e., the Chern number, of the parametric manifold. Since the Chern number is robust against perturbations to the system, the scheme is insensitive to the systematic errors of the control fields, the deviations of the modulation frequencies, and decoherence of the molecule. Therefore, the scheme may provide useful perspectives to construct a robust discriminator of chiral molecules.

Coherent manipulation of bright and dark solitons of reflection and transmission pulses through sodium atomic medium

Abstract The coherent manipulation and control of bright and dark solitons through sodium atomic medium have been investigated in this manuscript. Dark soliton is reported for reflection and bright soliton is reported for transmission pulses with variation in position and driving field parameters through sodium atomic medium. Further the transmission pulse is periodic dark and bright solitonic behaviors and reflection pulse is periodic bright solitonic behavior with variation in the incident angle and Rabi frequency of the control field. Elliptical dark and bright solitons as well as breather types solitons are also investigated for reflection and transmission pulses. The dark soliton in reflection is due to slow light propagation and bright soliton is obtained due to fast light propagation of transmission through the medium. The modified results of the dark and bright solitons are useful for telecommunication and ultra-fast signal routing system.

Individual Addressing and State Readout of Trapped Ions Utilizing Radio-Frequency Micromotion.

Excess "micromotion" of trapped ions due to the residual radio-frequency (rf) trapping field at their location is often undesirable and is usually carefully minimized. Here, we induce precise amounts of excess micromotion on individual ions by adjusting the local static electric field they experience. Micromotion modulates the coupling of an ion to laser fields, ideally tuning it from its maximum value to zero as the ion is moved away from the trap's rf null. We use tunable micromotion to vary the Rabi frequency of stimulated Raman transitions over two orders of magnitude, and to individually control the rates of resonant fluorescence from three ions under global laser illumination without any changes to the driving light fields. The technique is amenable to situations where addressing individual ions with focused laser beams is challenging, such as tightly packed linear ion strings or two-dimensional ion arrays illuminated from the side.

Phase sensitive slow light in semiconductor quantum dots

This article presents a theoretical investigation of phase-controlled propagation of slow light under an electromagnetically induced transparency window in a multilayered one-dimensional photonic crystal with semiconductor quantum dot nanostructures as defects. To achieve the electromagnetically induced transparency window, a setup utilizes a faint probe laser pulse alongside two powerful control laser beams arranged in a closed-loop cascade configuration. In this arrangement, a significant Kerr nonlinearity, approximately on the scale of ∼10−13m2/V2, is discerned within the quantum dot nanostructures at a probe wavelength of 1.55 μm. It is observed that both the amplitude and the phase relationship of the control Rabi frequencies play crucial roles in governing the dynamics of the group velocity of the probe field in the quantum dot nanostructures. Under the regime of electromagnetically induced transparency, the group velocity of the probe field is significantly reduced, approximately by a factor of 103 times as compared to the light speed in free space. These findings hold promise for potential applications in nonlinear optics.

Low-frequency weak electric field measurement based on Rydberg atoms using cavity-enhanced three photon system

Introduction: Rydberg atoms are ideal for measuring electric fields due to their unique physical properties. However, low-frequency electric fields below MHz can be challenging due to the accumulation of ionized free electrons on the atomic vapor cell’s surface, acting as a shield.Method: This paper proposes a Cavity-enhanced three-photon system (CETPS) measurement scheme, which uses a long-wavelength laser to excite the Rydberg state, reducing atomic ionization and enhancing detection spectrum resolution. A theoretical model is proposed to explain the quantum coherence effect of the light field, measured electric field, and the atomic system.Result: The results show that the proposed scheme significantly increases the electromagnetically induced transparency (EIT) spectral peak and narrows the spectral width, resulting in the maximum slope increasing by more than an order of magnitude.Discussion: The paper also discusses the impact of the Rabi frequency of the two laser fields and the coupling coefficient of the optical cavity on the transmission spectrum amplitude and linewidth, along with the optimal configuration of these parameters in the CEPTS scheme.

Natural non-Hermitian interaction alignment with photon-phonon quantization in Eu3+: NaYF4

We investigated the photon and phonon alignment for two dressing interaction profile in Eu+3: NaYF4. The evolution from strong to weak interaction alignment can be controlled by time gate width and time gate position, which shows that time gate position seems more sensitive than time gate width, while changing both can make interaction alignment oscillation due to two phonon and one photon quantization. Fluorescence FL signal switch from dip to peak interaction profile due to strong gamma, while the Super-Fluorescence SFWM signal switch from peak to dip interaction profile due to strong Rabi frequency (G). Comparing single laser spectral alignment to two-laser interaction alignment, the FL and SFWM shows dressing peak dip switch (spectral to interaction profile). In contrast, there is no switch in AT (spectral to interaction profile) because, the phase difference of the second laser balances the destructive and constructive dressing quantization’s. Such results can have potential applications in fine and hyper structure interaction alignment in non-polar ion.

Microcontroller-Optimized Measurement Electronics for Coherent Control Applications of NV Centers.

Long coherence times at room temperature make the NV center a promising candidate for quantum sensors and quantum computers. The necessary coherent control of the electron spin triplet in the ground state requires microwave π pulses in the nanosecond range, obtained from the Rabi oscillation of the mS spin states of the magnetic resonances of the NV centers. Laboratory equipment has a high temporal resolution for these measurements but is expensive and, therefore, uninteresting for fields such as education. In this work, we present measurement electronics for NV centers that are optimized for microcontrollers. It is shown that the Rabi frequency is linear to the output of the digital-to-analog converter (DAC) and is used to adapt the time length π of the electron spin flip, to the limited pulse width resolution of the microcontroller. This was achieved by breaking down the most relevant functions of conventional laboratory devices and replacing them with commercially available integrated components. The result is a cost-effective handheld setup for coherent control applications of NV centers.

Superadiabatic-based shortcuts for the fast generation of multi-partite W states of distant transmon qubits

We propose an efficient scheme for the fast generating three-partite W states of distant transmon qubits. With the help of superadiabatic shortcuts technology, we construct shortcuts to adiabaticity (STA) passage. The Rabi frequencies of the designed driving pulses in the scheme can be expressed by the superpositions of Gaussian functions. These make our scheme more feasible in the experiment. Compare with the adiabatic case, we show that the preparation of the target state can be greatly accelerated. We analyze the influences of decoherent factors on the fidelity of W states, and numerical results show our proposal is suitable to generate high fidelity three-partite W states. In addition, the present scheme can also be generalized to prepare n-partite W states of distant transmon qubits. This work may useful applications for the realization of distributed quantum computation.

Selective Transition Enhancement in a g-Engineered Diradical.

A diradical with engineered g-asymmetry was synthesized by grafting a nitroxide radical onto the [Y(Pc)2]⋅ radical platform. Various spectroscopic techniques and computational studies revealed that the electronic structures of the two spin systems remained minimally affected within the diradical system. Fluid-solution Electron Paramagnetic Resonance (EPR) experiments revealed a weak exchange coupling with |J| ~ 0.014 cm-1, subsequently rationalized by CAS-SCF calculations. Frozen solution continuous-wave (CW) EPR experiments showed a complicated and power-dependent spectrum that eluded analysis using the point-dipole model. Pulse EPR manipulations with varying microwave powers, or under varying magnetic fields, demonstrated that different resonances could be selectively enhanced or suppressed, based on their different tipping angles. In particular, Field-Swept Echo-Detected (FSED) spectra revealed absorptions of MW power-dependent intensities, while Field-Swept Spin Nutation (FSSN) experiments revealed two distinct Rabi frequencies. This study introduces a methodology to synthesize and characterize g-asymmetric two-spin systems, of interest in the implementation of spin-based CNOT gates.

Optical manipulation in Rubidium-87 atomic medium using Kerr field: Dynamic insights into two-interfering electromagnetic waves

In this manuscript, we investigate the intricate dynamical properties arising from the interaction of two-interfering electromagnetic waves within a Rubidium-87 four-level N-type atomic medium. The study employs a probe field to interact with the atomic medium while incorporating two control fields one of which would be the Kerr field to modulate the system dynamics. The key parameters under scrutiny include the probe field detuning (ΔP/γ), control field parameters such as Rabi frequencies and detunings (Ω1,2/γ, Δ1,2/γ), and the angular orientation (θ) between the two-interfering waves. The research delves into the Energy density W, Momentum density P, Spin Angular momentum density S, Absorption rate Arate, Gradient force Fgrad, and Torque T associated with the two-interfering waves within the atomic medium. Through systematic variations in the aforementioned parameters, significant insights are gained into the nuanced behaviour of the system. The results showcase a rich tapestry of variations in the dynamical properties, shedding light on the underlying physics governing the interaction of electromagnetic waves in this unique atomic medium. This investigation not only contributes to the fundamental understanding of the dynamics within complex atomic systems but also holds potential applications in fields such as quantum information processing and quantum optics. The findings of this manuscript pave the way for further exploration and utilization of these intricate phenomena in the realm of advanced technologies and quantum communication.

Modulation of Second-Order Sideband Efficiency in an Atom-Assisted Optomechanical System

We propose an efficient scheme to enhance the generation of optical second-order sidebands (OSSs) in an atom-assisted optomechanical system. The cavity field is coupled with a strong driving field and a weak probe field, and a control field is applied to the atom. We use the steady-state method to analyze the nonlinear interaction in the system, which is different from the traditional linear analysis method. The existence of an auxiliary three-level atom driven by the control field significantly enhances the generation of an OSS. It is found that the efficiency of the OSS can be effectively modulated by adjusting the Rabi frequency of the control field, optomechanical cooperativity and atomic coupling strength. Our scheme provides a promising solution for controlling light propagation and has potential application in quantum optical devices and quantum information networks.

Strong coupling between colloidal quantum dots and dielectric cavity investigated by both photoluminescence spectrum and reflection spectrum at room temperature

In this study, the angle-resolved photoluminescence spectra and reflection spectra from colloidal quantum dots on SiO2/Si material were investigated at room temperature. The strong coupling between quantum dots and F-P cavity was verified by both the photoluminescence spectral splitting and reflection dispersion. A Rabi splitting was obtained from both angle-resolved photoluminescence spectra and reflection spectra. The Hopfield coefficient of exciton and photon for polariton branches were calculated and analyzed. The relationship between Rabi frequency and excitation power for colloidal quantum dots was also studied. A method was proposed and used to characterize the cavity mode and the reflection dispersion by using open-aperture and close-aperture reflection spectra.

The Asymmetry Observed between the Effects of Photon-Phonon Coupling and Crystal Field on the Fine Structure of Fluorescence and Spontaneous Four-Wave Mixing in Ion-Doped Microcrystals.

In this paper, we explore the asymmetry observed between the effects of photon-phonon coupling (nested-dressing) and a crystal field (CF) on the fine structure of fluorescence (FL) and spontaneous four-wave mixing (SFWM) in Eu3+: BiPO4 and Eu3+: NaYF4. The competition between the CF and the strong photon-phonon dressing leads to dynamic splitting in two directions. The CF leads to static splitting in one direction under weak phonon dressing. The evolution from strong dressing to weak dressing results in spectral asymmetry. This spectral asymmetry includes out-of-phase FL and in-phase SFWM. Further, the large ratio between the dressing Rabi frequency and the de-phase rate leads to strong FL and SFWM asymmetry due to photon-phonon constructive dressing. Moreover, the experimental results suggest the analogy of a spectra asymmetry router with a channel equalization ratio of 96.6%.

Coherent manipulation of vectorial soliton beam in sodium like atomic medium

A four-level, sodium like atomic medium, driven by a probe and control fields, is used to modify the paraxial vectorial light beam in the medium. A uniform packet of vector arrows is controlled, whose shape is stable and undistorted during propagation, known as vectorial soliton. To the best of our knowledge, significant control over vectorial soliton is reported for the first time in the present work. Optical vectorial solitonic beams are controlled and manipulated with the parameters of the coupled fields with the system. The vectorial soliton is a strong, undistorted function of detunings, Rabi frequencies, and collective phase of the deriving fields, respectively. The modified vectorial solitons may have useful applications in telecommunication technology for delivering data bit streams over long distances and data processing.

Microscopic theory of nonlinear phase space filling in polaritonic lattices

We develop a full microscopic theory for a nonlinear phase space filling (NPSF) in strongly coupled two-dimensional polaritonic lattices. Ubiquitous in polaritonic experiments, the theoretical description of NPSF, also known as nonlinear optical saturation, remains limited to perturbative treatment and homogeneous samples. In this study, we go beyond the existing theoretical description and discover the broad scope of regimes where NPSF crucially modifies the optical response. Studying the quantum effects of non-bosonicity, cooperative light-matter coupling, and Coulomb blockade, we reveal several regimes for observing the nonlinear Rabi splitting quench due to the phase space filling. Unlike prior studies, we derive nonlinear Rabi frequency scaling all the way to the saturation limit and show that the presence of a lattice potential leads to qualitatively distinct nonlinearity. We concentrate on the three regimes of NPSF: (1) planar; (2) fractured; and (3) ultralocalized. For the planar saturation, the Rabi frequency decreases exponentially as a function of exciton density. For the fractured case, where excitons form a lattice with sites exceeding the exciton size, we discover fast NPSF at low occupations. This is followed by slower NPSF as the medium becomes fully saturated. This behavior is particularly pronounced in the presence of Coulomb (or Rydberg) blockade, where regions of fast and slow NPSF depend on the strength of repulsion. For the ultralocalized NPSF, we observe the square-root saturation typical to the collection of two-level systems. Our findings shed light on recent observations of strong nonlinearity in heterobilayers of transition metal dichalcogenides where moiré lattices emerge naturally []. Finally, the developed theory opens the prospects for engineering strongly nonlinear responses of polaritonic lattices with patterned samples, driving polaritonics into the quantum regime. Published by the American Physical Society 2024

Combining six superluminal and subluminal structured light fields with right and left circular polarizations in a chiral medium through superposition

The structured vector fields of circularly polarized light, comprising both left and right (RCP and LCP) beams superposed in the atomic medium are investigated in this work. At resonance in the anomalous/normal dispersion area, both RCP and LCP beams with a non-negative and non-positive group index of ±40 have been recorded. RCP and LCP beam group velocities are enhanced to ±1.5×109m/s at δ=0.15Γ, that is surpassing the speed of light in vacuum, denoted as ”c” leading to superluminal propagation. The RCP is superluminal and the LCP subluminal at the resonance point of the probe field. The group delay for The LCP beam is positive and the RCP beam is non-positive. The worth of the group delay for RCP and LCP beams varies to ±4ns. The superposing structured vectors field of superluminal and subluminal circularly polarized light beams on the right and left ER,L(r,φ) are strong variation function of detuning of probe field δ/Γ, Rabi frequency of control field Λ3/Γ and phase of collective driving fields φ. The results are useful for the modification of powerful computers.

Electric field dependence of spin qubit in a Si-MOS quantum dot

Abstract Valley, the intrinsic feature of silicon, is an inescapable subject in silicon-based quantum computing. At the spin–valley hotspot, both Rabi frequency and state relaxation rate are significantly enhanced. With protection against charge noise, the valley degree of freedom is also conceived to encode a qubit to realize noise-resistant quantum computing. Here, based on the spin qubit composed of one or three electrons, we characterize the intrinsic properties of valley in an isotopically enriched silicon quantum dot (QD) device. For one-electron qubit, we measure two electric-dipole spin resonance (EDSR) signals which are attributed to partial occupation of two valley states. The resonance frequencies of two EDSR signals have opposite electric field dependences. Moreover, we characterize the electric field dependence of the upper valley state based on three-electron qubit experiments. The difference of electric field dependences of the two valleys is 52.02 MHz/V, which is beneficial for tuning qubit frequency to meet different experimental requirements. As an extension of electrical control spin qubits, the opposite electric field dependence is crucial for qubit addressability, individual single-qubit control and two-qubit gate approaches in scalable quantum computing.

Coulomb effect in hybrid double quantum dot-metal nanoparticle systems considering the wetting layer

Many body effects in the wetting layer (WL)-double quantum dot (DQD)-metal nanoparticle (MNP) structure have been studied by modeling the Coulomb scattering rates in this structure. The strong coupling between WL-DQD-MNPs was considered. An orthogonalized plane wave (OPW) is assumed between WL-QD transitions. The transition momenta are calculated accordingly to specify the normalized Rabi frequency on this structure, considering the strong coupling between the WL-DQD-MNP structures. This approach is important for realizing scattering rates, including in-and-out capture and relaxation rates, which are essential for specifying the type of structure used depending on the optimum value of the scattering time required to fit the application. The QD hole capture rate is the highest, and the hole capture times are the shortest. The relaxation times are less than the electron capture times by one order, while they are half of the hole capture times. The capture rates increase with increasing distance R between the DQDs and the MNP. High tunneling increases hole-capture rates and changes the relaxation rates, showing the importance of tunneling in controlling the scattering rates.

Electrically Tunable Single Polaritonic Quantum Dot at Room Temperature.

Exciton-polaritons confined in plasmonic cavities are hybridized light-matter quasiparticles, with distinct optical characteristics compared to plasmons and excitons alone. Here, we demonstrate the electric tunability of a single polaritonic quantum dot operating at room temperature in electric-field tip-enhanced strong coupling spectroscopy. For a single quantum dot in the nanoplasmonic tip cavity with variable dc local electric field, we dynamically control the Rabi frequency with the corresponding polariton emission, crossing weak to strong coupling. We model the observed behaviors based on the quantum confined Stark effect in the strong coupling regime.