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Engineering bilinear mode coupling in circuit QED: Theory and experiment
摘要： Photonic states of high-Q superconducting microwave cavities controlled by superconducting transmon ancillas provide a platform for encoding and manipulating quantum information. A key challenge in scaling up the platform towards practical quantum computation is the requirement to communicate on demand the quantum information stored in the cavities. It has been recently demonstrated that a tunable bilinear interaction between two cavity modes can be realized by coupling the modes to a bichromatically driven superconducting transmon ancilla, which allows swapping and interfering the multiphoton states stored in the cavity modes [Gao et al., Phys. Rev. X 8, 021073 (2018)]. Here we explore both theoretically and experimentally the regime of relatively strong drives on the ancilla needed to achieve fast SWAP gates but which can also lead to undesired nonperturbative effects that lower the SWAP fidelity. We develop a theoretical formalism based on linear response theory that allows one to calculate the rate of ancilla-induced interaction, decay, and frequency shift of the cavity modes in terms of a susceptibility matrix. We go beyond the usual perturbative treatment of the drives by using Floquet theory, and find that the interference of the two drives can strongly alter the system dynamics even in the regime where the standard rotating wave approximation applies. The drive-induced ac Stark shift on the ancilla depends nontrivially on the drive and ancilla parameters which in turn modify the strength of the engineered interaction. We identify two major sources of infidelity due to ancilla decoherence. (i) Ancilla dissipation and dephasing lead to incoherent hopping among Floquet states which occurs even when the ancilla is at zero temperature; this hopping results in a sudden change of the SWAP rate, thereby decohering the SWAP operation. (ii) The cavity modes inherit finite decay from the relatively lossy ancilla through the inverse Purcell effect; the effect becomes particularly strong when the ac Stark shift pushes certain ancilla transition frequencies to the vicinity of the cavity mode frequencies. The theoretical predictions agree quantitatively with the experimental results, paving the way for using the developed theory for optimizing future experiments and architecture designs.
关键词： decoherence,transmon ancilla,superconducting cavities,ac Stark shift,quantum information,circuit QED,inverse Purcell effect,bilinear mode coupling,SWAP gates,Floquet theory
更新于2025-09-23 15:23:52
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Integral Method Analysis of Electroabsorption Spectra and Electrophotoluminescence Study of (C <sub/>4</sub> H <sub/>9</sub> NH <sub/>3</sub> ) <sub/>2</sub> Pbl <sub/>4</sub> Organic–Inorganic Quantum Well
摘要： Electric-field-induced changes in absorption and photoluminescence (PL) spectra and in PL decay profile have been measured for two-dimensional hybrid organic?inorganic halide perovskite semiconductor, ((C4H9NH3)2Pbl4) (N1). Electro-absorption (E-A) spectra observed at room temperature and at a low temperature of 45 K were analyzed by assuming the Stark shift, and the magnitudes of the change in electric dipole moment and polarizability following photoexcitation were determined. The strong signal observed in the E-A spectra at 45 K was interpreted in terms of the weak absorption band which shows extremely large Stark shift resulting from the large change in polarizability following photoexcitation. Electrophotoluminescence spectra of this compound, that is, field-induced change in PL spectra, show that PL of N1 is quenched by the application of electric field. Field effects on PL decay profiles show that the quenching results both from the field-induced decrease of the population of the emitting state following photoexcitation and from the field-induced lifetime shortening caused by the enhancement of the nonradiative decay rate at the emitting state. At a low temperature of 45 K, two exciton emissions, each of which originates from different phase, appear, and both emissions are quenched by the applied electric field with different efficiencies from each other. It is also found that trap emissions observed at low temperature in the wavelength region longer than the sharp exciton bands show more efficient field-induced quenching than that of the exciton emissions, suggesting that energy transfer from the photoexcited state to trapped states is decelerated by the applied electric field.
关键词： Electrophotoluminescence,Electroabsorption,Perovskite,Stark Shift,Quantum Well
更新于2025-09-23 15:21:21
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Quantum-memory-enabled ultrafast optical switching in carbon nanotubes
摘要： Optical nonlinearities can be engineered into high-speed optical gates when a probe signal is switched coherently and fast by an optical control pulse through various nonlinear effects for switching. In semiconductors, strong light–matter interaction can also excite many electrons to interact with each other, which can deteriorate switching through Coulomb-induced dephasing. Here, we demonstrate that optical transmission of carbon nanotubes can be switched reversibly hundreds of times via detuned Rabi splitting, faster than 200 fs via nonresonant but strong control pulses. Our detailed experiment–theory analysis identifies that quantum memory in Coulombic scattering restores reversibility whilst simultaneously reducing undesirable pure dephasing of coherences. This capability creates new possibilities for ultrafast quantum optoelectronic processing in quantum materials.
关键词： carbon nanotubes,Ultrafast switching,quantum memory of many-body nonlinearilties,excitonic Stark shift,quantum optoelectronics
更新于2025-09-23 15:21:01
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Measurement of Molecular Transition Frequencies with the Uncertainties Lower Than 10 <sup>?17</sup>
摘要： Precise measurement of atomic transition frequencies (neutral, ion) have been performed and the uncertainty of the order of 10-18 has been attained with several transitions. However, the measurement uncertainty lower than 10-15 has never been attained with molecular transition frequencies. Precise measurement of molecular transition frequencies are useful to develop physics beyond the standard model: detection of electron electric dipole moment, detection of symmetry violation between optical isomers of chiral molecules, and search for the variation in the proton-to-electron mass ratio etc.. The attained systematic frequency is limited by the Stark, Zeeman, and electric quadrupole shifts, which have significant dependence on the electronic states and the angular momentum quantum numbers (electron orbital angular momentum, spin, nuclear spin, molecular rotation, and couplings between them). The molecular pure vibrational transition frequencies without changing any angular momentum quantum numbers are expected to be advantageous for precise measurement, because all frequency shifts at upper and lower states are more than 99 % canceled. Theoretical estimation of attainable accuracies will be given in this presentation.
关键词： electric quadrupole shift,precise measurement,uncertainty,Zeeman shift,Stark shift,molecular transition frequencies
更新于2025-09-12 10:27:22
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Exciton-phonon properties in cylindrical quantum dot with parabolic confinement potential under electric field
摘要： The mixed confinement potential effect on exciton in cylindrical quantum dot (QD) is calculated in the presence of an electric field with and without confined longitudinal optical (LO) phonon mode contribution. The variational approach within the effective mass approximation is used to describe the exciton-phonon interaction with three variational parameters of the trial wave function. The ground state binding energy of exciton has been calculated numerically for the parabolic (axial direction) and square (lateral direction) finite confinement potentials under the electric field applied along the growth direction of the QD. The system both with and without LO-phonon contribution is investigated. The combined effects of applied electric field and parabolic confinement on the ground state binding energy, the polaronic correction and the Stark shift are examined in detail. The findings indicate that the electric field strongly reduces the binding energy in both ignoring and considering LO-phonon interaction especially for wider thickness of QD. We have shown that the contribution of LO-phonon leads to an increase in the binding energy and to decrease in the Stark shift energy. Furthermore, our numerical results illustrate a strong dependence of Stark shift on the QD height, electric field strength and LO-phonon contribution.
关键词： Parabolic potential,Electric field,Binding energy,Exciton-LO-phonon,Stark shift
更新于2025-09-12 10:27:22
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ac Stark shifts of dark resonances probed with Ramsey spectroscopy
摘要： The off-resonant ac Stark shift for coherent population trapping (CPT) resonances probed with Ramsey spectroscopy is investigated experimentally and theoretically. Measurements with laser-cooled 87Rb atoms show excellent quantitative agreement with a simple theory. The shift depends on the relative intensity of the two CPT light fields, but depends only weakly on the total intensity. Since the origin of the shift is through couplings of the interrogation light to off-resonant excited-state hyperfine levels, the size and sign of the shift depend on the specific interrogation scheme. The theory also shows that for several commonly used interrogation schemes it is possible to minimize the off-resonant light shift or its dependence on the CPT intensity ratio by properly selecting the system parameters.
关键词： hyperfine levels,laser-cooled atoms,coherent population trapping,ac Stark shift,Ramsey spectroscopy
更新于2025-09-10 09:29:36
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Precise Measurement of Transition Frequencies of Optically Trapped <sup>40</sup> Ca <sup>19</sup> F Molecules
摘要： The laser cooling and trapping of molecules have recently been achieved. In this paper, the possibility of precisely measuring the vibrational transition frequencies of optically trapped 40Ca19F molecules is discussed. The quadratic Stark shift induced by the trap laser is eliminated using the trap laser frequencies where the Stark energy shifts at upper and lower states are equal (magic frequencies). At one value of the magic frequency, molecules are trapped at the positions where the power density is minimum, therefore, the measurement is not sensitive to the detuning of the trap laser frequency from the magic frequency. Measurement with an uncertainty of 10?17 appears to be possible using the ev; N; J; F; MT ? e0; 0; 1=2; 1; (cid:2)1T ! e1; 0; 1=2; 1; (cid:2)1T transition frequency.
关键词： laser cooling,Stark shift,magic frequencies,molecules,vibrational transition frequencies,trapping
更新于2025-09-04 15:30:14
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Nonresonant photons catalyze photodissociation of phenol
摘要： Phenol represents an ideal polyatomic system for demonstrating photon catalysis because of its large polarizability, well-characterized excited-state potential energy surfaces, and nonadiabatic dissociation dynamics. A nonresonant IR pulse (1064 nm) supplies a strong electric field (4 x 107 V/cm) during the photolysis of isolated phenol (C6H5OH) molecules to yield C6H5O + H near two known energetic thresholds: the S1/S2 conical intersection and the S1 - S0 origin. H-atom speed distributions show marked changes in the relative contributions of dissociative pathways in both cases, compared to the absence of the nonresonant IR pulse. Results indicate that nonresonant photons lower the activation barrier for some pathways relative to others by dynamically Stark shifting the excited-state potential energy surfaces rather than aligning molecules in the strong electric field. Theoretical calculations offer support for the experimental interpretation.
关键词： phenol,photodissociation,dynamic Stark shift,photon catalysis,nonresonant IR field
更新于2025-09-04 15:30:14
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Stark shift of excitons and trions in two-dimensional materials
摘要： The effect of an external in-plane electric ?eld on neutral and charged exciton states in two-dimensional (2D) materials is theoretically investigated. These states are argued to be strongly bound, so that electron-hole dissociation is not observed up to high electric ?eld intensities. Trions in the anisotropic case of monolayer phosphorene are demonstrated to be especially robust under electric ?elds, so that ?elds as high as 100 kV/cm yield no signi?cant effect on the trion binding energy or probability density distribution. Polarizabilities of excitons are obtained from the parabolicity of numerically calculated Stark shifts. For trions, a fourth order Stark shift is observed, which enables the experimental veri?cation of hyperpolarizability in 2D materials, as observed in the highly excited states of the Rydberg series of atoms and ions.
关键词： Stark shift,polarizability,two-dimensional materials,electric field,excitons,trions,hyperpolarizability
更新于2025-09-04 15:30:14
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State-Resolved Probing of Attosecond Timescale Molecular Dipoles
摘要： We report an experimental study of iodomethane attosecond transient absorption spectroscopy (ATAS) in the region of iodine 4d core-to-valence/Rydberg excitation. Similar to previous atomic experiments, XUV-NIR delay-dependent absorbance changes reflect a light-induced phase due to an NIR-field driven AC Stark shift of the excited states, as well as pathway interferences arising from couplings between neighboring states. As a novel aspect of molecular ATAS, we observe pronounced differences between the ATAS signatures of valence and Rydberg states. While the core-to-valence transitions carry the majority of the XUV oscillator strength, the core-to-Rydberg transitions are dominantly affected by a moderately strong, non-ionizing NIR field. Our experimental findings are corroborated by ab-initio calculations and ATAS simulations.
关键词： core-to-valence,attosecond transient absorption spectroscopy,iodomethane,core-to-Rydberg,AC Stark shift,ab-initio calculations,XUV-NIR
更新于2025-09-04 15:30:14