Multiphoton Transitions Research Articles

Electrical manipulation of the spins in phosphorene double quantum dots

We investigate electric dipole spin resonance (EDSR) induced by an oscillating electric field within a system of double quantum dots formed electrostatically in monolayer phosphorene. Apart from the observed anisotropy of effective masses, phosphorene has been predicted to exhibit anisotropic spin-orbit coupling. Here, we examine a system consisting of two electrons confined in double quantum dots. A single-band effective Hamiltonian together with the configuration interaction theory is implemented to simulate the time evolution of the ground state. We examine spin flips resulting from singlet-triplet transitions driven by external AC electric fields, both near and away from the Pauli blockade regime, revealing fast sub-nanosecond transition times. Furthermore, we analyze the impact of anisotropy by comparing dots arranged along a different crystal axis. The sub-harmonic multi-photon transitions and Landau-Zener-Stückelberg-Majorana transitions are discussed. We show modulation of spin-like and charge-like characteristics of the qubit through potential detuning.

Time-dependent theory of reconstruction of attosecond harmonic beating by interference of multiphoton transitions

Time-dependent theory of reconstruction of attosecond harmonic beating by interference of multiphoton transitions

Quantum Fisher information and entanglement of a dissipative hybrid optomechanical system with multi-photon transition

Quantum Fisher information and entanglement of a dissipative hybrid optomechanical system with multi-photon transition

Ultrafast quantum control of atomic excited states via interferometric two-photon Rabi oscillations

Quantum-state manipulation through coherent interaction with a radiation field is a fundamental process with broad implications in quantum optics and quantum information processing. However, current quantum control methods are limited by their operation at Rabi frequencies below the gigahertz range, which restricts their applicability to systems with long coherence times. To overcome this limitation, alternative approaches utilizing ultrafast driving lasers have garnered great interest. In this work, we demonstrate two-photon Rabi oscillations in the excited states of argon operating at terahertz frequencies driven by ultrafast laser pulses. Leveraging quantum-path interferometry, we are able to measure and manipulate both the amplitudes and phases of the transition dipoles by exploiting the intensity and polarization state of the driving laser. This precise control enables femtosecond population transfer and coherent accumulation of geometric phase. Our findings provide valuable insights into the all-optical manipulation of extreme-ultraviolet radiations and demonstrate the possibility of ultrafast quantum control through interferometric multiphoton transitions.

On the nature of two-photon transitions for a collection of molecules in a Fabry-Perot cavity.

We investigate the effect of a cavity on nonlinear two-photon transitions of a molecular system and we analyze how such an effect depends on the cavity quality factor, the field enhancement, and the possibility of dephasing. We find that the molecular response to strong light fields in a cavity with a variable quality factor can be understood as arising from a balance between (i) the ability of the cavity to enhance the field of an external probe and promote multiphoton transitions more easily and (ii) the fact that the strict selection rules on multiphoton transitions in a cavity support only one resonant frequency within the excitation range. Although our simulations use a classical level description of the radiation field (i.e., we solve Maxwell-Bloch or Maxwell-Liouville equations within the Ehrenfest approximation for the field-molecule interaction), based on experience with this level of approximation in the past studies of plasmonic and polaritonic systems, we believe that our results are valid over a wide range of external probing.

Adiabatic elimination in the presence of multiphoton transitions in atoms inside a cavity

Various approaches have been used in the literature for eliminating nonresonant levels in atomic systems and deriving effective Hamiltonians. Important among these are elimination techniques at the level of probability amplitudes, operator techniques to project the dynamics on to the subspace of resonant levels, Green’s function techniques, the James’ effective Hamiltonian approach, etc. None of the previous approaches is suitable for deriving effective Hamiltonians in intracavity situations. However, the James’ approach does work in the case of only two-photon transitions in a cavity. A generalization of the James’ approach works in the case of three-photon transitions in a cavity, but only under Raman-like resonant conditions. Another important approach for adiabatic elimination is based on an adaptation of the Markov approximation well-known in the theory of system–bath interactions. However, this approach has not been shown to work in intracavity situations. In this paper, we present a method of adiabatic elimination for atoms inside cavities in the presence of multiphoton transitions. We work in the Heisenberg picture, and our approach has the advantage that it allows one to derive effective Hamiltonians even when Raman-like resonance conditions do not hold.

Enhancement of Entanglement via Incoherent Collisions.

In contrast to the general thought that the collisions are intrinsically dephasing in nature and detrimental to quantum entanglement at room or higher temperatures, here, we show that in the conventional ladder-type electromagnetically induced transparency (EIT) configuration, when the probe field intensity is not very weak as compared to the pump field, the entanglement between the bright pump and probe fields can be remarkably enhanced with the increase of the collisional decay rates in a moderate range in an inhomogeneously broadened atomic system. The strengthened entanglement results from the enhancement of constructive interference and suppression of destructive interference between one-photon and multiphoton transition pathways. Our results clearly indicate that the collisions offer a promising alternative to enhance entanglement at room or higher temperatures despite of the dephasing nature, which provides great convenience for experimental implementation, and opens new prospects and applications in realistic quantum computation and quantum information processing.

First-order crosstalk mitigation in parallel quantum gates driven with multi-photon transitions

We demonstrate an order of magnitude reduction in the sensitivity to optical crosstalk for neighboring trapped-ion qubits during simultaneous single-qubit gates driven with individual addressing beams. Gates are implemented via two-photon Raman transitions, where crosstalk is mitigated by offsetting the drive frequencies for each qubit to avoid first-order crosstalk effects from inter-beam two-photon resonance. The technique is simple to implement, and we find that phase-dependent crosstalk due to optical interference is reduced on the most impacted neighbor from a maximal fractional rotation error of 0.185(4) without crosstalk mitigation to ≤0.006 with the mitigation strategy. Furthermore, we characterize first-order crosstalk in the two-qubit gate and avoid the resulting rotation errors for the arbitrary-axis Mølmer–Sørensen gate via a phase-agnostic composite gate. Finally, we demonstrate holistic system performance by constructing a composite CNOT gate using the improved single-qubit gates and phase-agnostic two-qubit gate. This work is done on the Quantum Scientific Computing Open User Testbed; however, our methods are widely applicable for individual addressing Raman gates and impose no significant overhead, enabling immediate improvement for quantum processors that incorporate this technique.

Geometric phase and Wehrl phase entropy for two superconducting qubits in a coherent field system under the effect of nonlinear medium

In this paper, we study the dynamical behavior of coherence, geometric phase, Wehrl entropy (WE) for a quantum model consisting of two superconducting qubits (SC–Qs) in the presence of multi-photon transition. We develop the Hamiltonian model and solve the Schrödinger equation that leads to evaluate the density matrix of whole system as well as subsystems. We introduce the effects of nonlinearity and subsystems interaction and display the temporal behavior of different quantumness measures in the existence and absence of nonlinear Kerr medium and Ising interaction.

Multiphoton hyperfine Raman transitions with different quantization axes

Multiphoton hyperfine Raman transitions with different quantization axes

Enhancing the atomic correlation dynamics under the effects of Stark shift and Kerr medium through multi-photon transitions

Enhancing and preserving the atomic correlation and entanglement is of significant utility in quantum information. To this aim, we study the temporal evolution of uncertainty-induced nonlocality ([Formula: see text]) and logarithmic negativity ([Formula: see text]) as measures of quantum correlations (QCs) and quantum entanglement (QE) between two effective atoms coupled to a bosonic reservoir in the absence of thermal fluctuations and in the presence of Kerr medium (KM) and Stark shift (SS) under which n-photon transitions are permitted. We explore how Markovian and non-Markovian regimes affect the temporal dynamics of atomic correlation and entanglement and its limitations. Our findings indicate that by adjusting the KM and SS parameters, the quantum correlations between the two atoms can be enhanced and maintained while displaying similar qualitative behavior. Notably, it was observed that the QCs and QE quantities are at their highest magnitudes in the non-Markovian regime when the strengths of both SS and KM are increased, implying that QCs and QE are well protected. In contrast to the typical view that protecting the QCs from decoherence that may be observed owing to environmental noise, we proposed a gainful way to reduce the atomic decoherence by adjusting the number of n-photon transitions. Our investigation reveals that in the non-Markovian regime, the considered system exhibits better resistance against decoherence in comparison to the Markovian regime, as evidenced by the significant amount of quantum correlations detected among the two effective atoms at a specific point in time.

The effect of intrinsic decoherence on the dynamics of an Ξ-type qutrit system interacting with a coherent field

This paper solves milburn’s intrinsic noise (IN) model for a 3-level atom of an Ξ-type interacting with a coherent cavity field via multiphoton transitions. Therefore, the effects of the intrinsic noise and the multi-photon interactions are investigated for some quantum phenomena, such as total correlation, entanglement, and atomic inversion. In general, we found that the collapse-revival phenomenon occurs during the oscillatory behaviour of atomic population dynamics. In addition, the birth-death phenomenon is observed in the negativity dynamics. Entropy, negativity, and mutual information have various dynamics. It is found that, as the entropy increases, the negativity and mutual information diminish to stationary levels. When intrinsic noise is considered, all the phenomena of atomic inversion, entropies, negativity and mutual information exhibit high sensitivity to high intrinsic noise values, except the mutual information dynamics, which is more resistant than that of the other quantifiers.

Ionization transition rates in the intermediate regime of the Keldysh parameter for a (0,1)*LG spiral amplitude modulated laser field

The mechanisms of the tunnel and multiphoton ionization transitions of hydrogen-like atoms and noble gas atoms are discussed. Atoms potassium and argon, with ionization energy of 4.34 and 15.76 eV, were chosen as the target. The atoms are exposed to Ti:Sapphire, (0,1)*LG, spiral amplitude modulated, laser beam at λ = 800 nm wavelength in a broad intensity range 1012 to 1015 W/cm2. The computational approach to describe tunnel and multiphoton processes was based on using the ADK theory. Stark and ponderomotive effects are also included to study their influence on the transition rate. Obtained results show that, for the lower γ values, the contribution of multiphoton ionization was less significant than the tunnel ionization contribution. In comparison, for higher γ values, multiphoton ionization dominated over tunnel ionization in a total transition rate. It is found that, in this particular case of spiral amplitude modulated mode, the intermediate regime, where both processes equally contribute, strongly depends on the atom selection and laser field intensity. Ionization in the intermediate regime occurs for γ ≈ 10 and 12 for low laser intensities, as γ ≈ 2 and 2.5 for the higher values, in the case of potassium and argon respectively. Our analysis indicated that the Stark and ponderomotive effects have a significant influence on the total transition rate. It is shown that these effects decrease the transition rate value and move the intermediate regime’s position toward lower values of the γ parameter, mainly in the case of higher laser field intensity.

Enhancement of the spectral broadening efficiency for circular polarization states in the high absorption regime for Gaussian and doughnut-shaped beams in fused silica.

We experimentally investigate the spectral broadening in fused silica in the multiphoton absorption regime. Under standard conditions of laser irradiation, linear polarization of laser pulses is more advantageous for supercontinuum generation. However, with high non-linear absorption, we observe more efficient spectral broadening for circular polarizations for both Gaussian and doughnut-shaped beams. The multiphoton absorption in fused silica is studied by measuring the total transmission of laser pulses and by the intensity dependence of the self-trapped exciton luminescence observation. The strong polarization dependence of multiphoton transitions fundamentally affects the broadening of the spectrum in solids.

Probing the Jaynes-Cummings Ladder with Spin Circuit Quantum Electrodynamics.

We report observations of transitions between excited states in the Jaynes-Cummings ladder of circuit quantum electrodynamics with electron spins (spin circuit QED). We show that unexplained features in recent experimental work correspond to such transitions and present an input-output framework that includes these effects. In new experiments, we first reproduce previous observations and then reveal both excited-state transitions and multiphoton transitions by increasing the probe power and using two-tone spectroscopy. This ability to probe the Jaynes-Cummings ladder is enabled by improvements in the coupling-to-decoherence ratio, and shows an increase in the maturity of spin circuit QED as an interesting platform for studying quantum phenomena.

The symmetry in the model of two coupled Kerr oscillators leads to simultaneous multi-photon transitions

We consider the model of two coupled oscillators with Kerr nonlinearities in the rotating-wave approximation. We demonstrate that for a certain set of parameters of the model, the multi-photon transitions occur between many pairs of the oscillator states simultaneously. Also, the position of the multi-photon resonances does not depend on the coupling strength between two oscillators. We prove rigorously that this is a consequence of a certain symmetry of the perturbation theory series for the model. In addition, we analyse the model in the quasi-classical limit by considering the dynamics of the pseudo-angular momentum. We identify the multi-photon transitions with the tunnelling transitions between the degenerate classical trajectories on the Bloch sphere.

Nonclassical correlations in lossy cavity optomechanics with intensity-dependent coupling

In this paper, we describe a double-optomechanical system which contains two lossy cavities, where each cavity includes a single-mode quantized field coupled to a single vibrational mode of a flexible membrane. There exists an interaction between a two-level atom and the cavity mode in the rotating wave approximation, with degenerate multi-photon transition in the presence of intensity-dependent coupling. Furthermore, we consider the effect of different sources of dissipation consisting of cavity decay, losses of cavity mirror, and spontaneous emission from the atom. We then start with the master equation to study the dynamics of considered quantum system. Afterward, we show that under some circumstances, the solution of the complicated problem via the master equation is reduced to the determination of the state vector in the time-dependent Schrödinger equation, with the help of an effective non-Hermitian Hamiltonian. Obtaining the explicit form of the state vector of the entire system, we study the nonclassical correlations of two atoms by means of geometric discord. We also examine the roles of intensity-dependent nonlinearity function, number of photons contributed to atomic transition, number of photons in the Fock states, and different sources of dissipation in the dynamics of geometric discord of the atoms. The numerical results indicate that the steady-state value of geometric discord can be revealed, and can appropriately be controlled via the mentioned-above effects. It can be found that the existence of spontaneous emission not only protects the nonclassical correlations of the atoms but also tends the geometric discord to a steady-state value.

Majorization ladder in bosonic Gaussian channels

We show the existence of a majorization ladder in bosonic Gaussian channels, that is, we prove that the channel output resulting from the nth energy eigenstate (Fock state) majorizes the channel output resulting from the (n+1)th energy eigenstate (Fock state). This reflects a remarkable link between the energy at the input of the channel and a disorder relation at its output as captured by majorization theory. This result was previously known in the special cases of a pure-loss channel and quantum-limited amplifier, and we achieve here its non-trivial generalization to any single-mode phase-covariant (or -contravariant) bosonic Gaussian channel. The key to our proof is the explicit construction of a column-stochastic matrix that relates the outputs of the channel for any two subsequent Fock states at its input. This is made possible by exploiting a recently found recurrence relation on multiphoton transition probabilities for Gaussian unitaries [Jabbour and Cerf, Phys. Rev. Res. 3, 043065 (2021)]. Possible generalizations and implications of these results are then discussed.

Extending Photocatalyst Activity through Choice of Electron Donor.

Sacrificial additives are commonly employed in photoredox catalysis as a convenient source of electrons, but what occurs after electron transfer is often overlooked. Tertiary alkylamines initially form radical cations following electron transfer, which readily deprotonate to form strongly reducing, neutral α-amino radicals. Similarly, the oxalate radical anion (C2O4•-) rapidly decomposes to form CO2•- (E0 ≈ -2.2 V vs SCE). We show that not only are these reactive intermediates formed under photoredox conditions, but they can also impact the desired photochemistry, both positively and negatively. Photoredox systems using oxalate as an electron donor are able to engage substrates with greater energy demands, extending reactivity past the energy limits of single and multiphoton transition metal catalysts. Furthermore, oxalate offers better chemoselectivity than the commonly employed triethylamine when reducing substrates with moderate energy requirements.

A multiphoton transition activated iron based metal organic framework for synergistic therapy of photodynamic therapy/chemodynamic therapy/chemotherapy for orthotopic gliomas.

Although photodynamic therapy (PDT) has exhibited good potential in therapy of gliomas, the limited penetration depth of light and the obstacle of the blood-brain barrier (BBB) lead to unsatisfactory treatment effects. Herein, a multifunctional nanodrug (UMD) was constructed with up-conversion nanoparticles (NaGdF4:Yb,Tm@NaYF4:Yb,Nd@NaYF4, UCNPs) as the core, the photosensitizer NH2-MIL-53 (Fe) as the shell and a carrier for loading chemotherapy drug doxorubicin hydrochloride (Dox) for synergistic therapy of gliomas. Lactoferrin (LF) was finally modified on the surface of the UMD to endow it with the ability to traverse the BBB and target cells (UMDL). The UCNP core can convert 808 nm near-infrared (NIR) light to ultraviolet light (UV light) for exciting NH2-MIL-53 (Fe), achieving NIR-mediated PDT. In addition, Fe3+ on the surface of the NH2-MIL-53 (Fe) shell could be reduced to Fe2+ in a tumor microenvironment (TME), and then reacted with over-expressed H2O2 in the TME to generate hydroxyl radicals (˙OH) for chemodynamic therapy (CDT). The Dox drug could be released in response to acidic conditions in the TME, inhibiting the growth of gliomas with low side effects. The synergistic effect of PDT/CDT/chemotherapy leads to effective suppression of orthotopic gliomas.