Regime Of Light-matter Interaction Research Articles

Parity-dependent State Engineering and Tomography in the ultrastrong coupling regime.

Reaching the strong coupling regime of light-matter interaction has led to an impressive development in fundamental quantum physics and applications to quantum information processing. Latests advances in different quantum technologies, like superconducting circuits or semiconductor quantum wells, show that the ultrastrong coupling regime (USC) can also be achieved, where novel physical phenomena and potential computational benefits have been predicted. Nevertheless, the lack of effective decoupling mechanism in this regime has so far hindered control and measurement processes. Here, we propose a method based on parity symmetry conservation that allows for the generation and reconstruction of arbitrary states in the ultrastrong coupling regime of light-matter interactions. Our protocol requires minimal external resources by making use of the coupling between the USC system and an ancillary two-level quantum system.

Breakthroughs in Photonics 2014: Random Lasers

Multiple scattering of light in a disordered medium with gain may provide for the necessary feedback to achieve lasing action without an optical cavity. In addition to the fundamental interest raised by this regime of light-matter interaction in open cavity, the relatively simple design of these so-called “random lasers” and the possibility to control their emission open perspective of new applications in domains not yet covered by conventional lasers.

Scalable quantum memory in the ultrastrong coupling regime.

Circuit quantum electrodynamics, consisting of superconducting artificial atoms coupled to on-chip resonators, represents a prime candidate to implement the scalable quantum computing architecture because of the presence of good tunability and controllability. Furthermore, recent advances have pushed the technology towards the ultrastrong coupling regime of light-matter interaction, where the qubit-resonator coupling strength reaches a considerable fraction of the resonator frequency. Here, we propose a qubit-resonator system operating in that regime, as a quantum memory device and study the storage and retrieval of quantum information in and from the Z2 parity-protected quantum memory, within experimentally feasible schemes. We are also convinced that our proposal might pave a way to realize a scalable quantum random-access memory due to its fast storage and readout performances.

Ultrastrong coupling in the near field of complementary split-ring resonators

The ultrastrong light-matter interaction regime was investigated in metallic and superconducting complementary split ring resonators coupled to the cyclotron transition of two dimensional electron gases. The sub-wavelength light confinement and the large optical dipole moment of the cyclotron transition yield record high normalized coupling rates of up to $\frac{\Omega_R}{\omega_c}=$ 0.87. We observed a blue-shift of both polaritons due to the diamagnetic term of the interaction Hamiltonian.

Hungry cavities

A microcavity device operating in the strong light–matter interaction regime can produce coherent perfect absorption of photons — providing a viable system for the perfect feeding of polaritons.

High-field terahertz bulk photovoltaic effect in lithium niobate.

The terahertz (THz) response of the ferroelectric prototype material lithium niobate (LiNbO3) is studied in the nonperturbative regime of light-matter interaction. Applying two-dimensional THz spectroscopy with few-cycle pulses of an amplitude E≈100 kV/cm and a center frequency of 2THz, we dissect the overall nonlinear response into different orders in the electric field. The underlying nonlinear current is of interband character and consists of a strong low-frequency shift current (SC) and higher harmonics of the THz fundamental. The SC component originates from the lack of inversion symmetry and the strong interband decoherence for long electron trajectories in k space as shown by theoretical calculations.

Recipe for the Hamiltonian of system-environment coupling applicable to the ultrastrong-light-matter-interaction regime

When the light interacts with matters in a lossy cavity, in the standard cavity quantum electrodynamics, the dissipation of cavity fields is characterized simply by the strengths of the two couplings: the light-matter interaction and the system-environment coupling through the cavity mirror. However, in the ultrastrong light-matter interaction regime, the dissipation depends also on whether the two couplings are mediated by the electric field or the magnetic one (capacitive or inductive in superconducting circuits). Even if we know correctly the microscopic mechanism (Lagrangian) of the system-environment coupling, the coupling Hamiltonian itself is in principle modified due to the ultrastrong interaction in the cavity. In this paper, we show a recipe for deriving a general expression of the Hamiltonian of the system-environment coupling, which is applicable even in the ultrastrong light-matter interaction regime in the good-cavity and independent-transition limit.

Mixed regime of light-matter interaction revealed by phase sensitive measurements of the dynamical Franz-Keldysh effect

Significant changes of the optical properties of semiconductors can be observed by applying strong electric fields capable to modify the band structure at equilibrium. This is known as the Franz-Keldysh effect (FKE). Here we study the FKE in bulk GaAs by combining single cycle THz pumps and broadband optical probes. The experiments show that the phase content of the selected electromagnetic pulses can be used to measure the timescales characteristic for the different regimes of matter-light interactions. Furthermore, the present phase-resolved measurements allow to identify a novel regime of saturation where memory effects are of relevance.

Surface plasmons and strong light-matter coupling in metallic nanoshells

A theory of the interaction between a radiating dipole and the plasmonic excitations of a spherical metallic nanoshell in the quasistatic approximation is formulated. After a derivation of surface plasmon frequencies and a comparison with the corresponding modes of metal spheres and cavities, we introduce an expression for the effective volume for any position of the dipole inside or outside the nanoshell, describing the local electromagnetic field enhancement in analogy to other cavity-QED systems. The modification of the dipole decay rate is calculated as a function of frequency for various geometrical parameters, and it reflects the spectrum of spherelike and cavity-like surface plasmon excitations. We then give a formulation of emission spectra, suitable for describing light-matter interaction beyond perturbation theory, and study the conditions for the strong coupling regime to occur. By suitably tuning the geometrical parameters of the nanoshell and by choosing the order of surface plasmon modes to minimize the effective volume, a vacuum Rabi splitting can occur in emission spectra for dipole oscillator strengths as small as a few units, which can be easily achieved with organic molecules or quantum dots. The most favorable situation for strong coupling is when the dipole is located inside the nanoshell. Surprisingly, this dipole couples with spherelike modes more strongly than with cavity-like ones, if the shell is thin enough. As a conclusion, metallic nanoshells turn out to be a suitable platform in order to investigate the strong-coupling regime of light-matter interaction by exploiting surface plasmon resonances.

Quantum Simulation of the Ultrastrong-Coupling Dynamics in Circuit Quantum Electrodynamics

We propose a method to get experimental access to the physics of the ultrastrong (USC) and deep strong (DSC) coupling regimes of light-matter interaction through the quantum simulation of their dynamics in standard circuit QED. The method makes use of a two-tone driving scheme, using state-of-the-art circuit-QED technology, and can be easily extended to general cavity-QED setups. We provide examples of USC/DSC quantum effects that would be otherwise unaccessible.

Ultrafast Quantum Gates in Circuit QED

We present a method to implement ultrafast two-qubit gates valid for the ultrastrong coupling and deep strong coupling regimes of light-matter interaction, considering state-of-the-art circuit quantum electrodynamics technology. Our proposal includes a suitable qubit architecture and is based on a four-step sequential displacement of the intracavity field, operating at a time proportional to the inverse of the resonator frequency. Through abinitio calculations, we show that these quantum gates can be performed at subnanosecond time scales while keeping a fidelity above 99%.

Intersubband polaritons in the electrical dipole gauge

We provide a theoretical description for the coupling between the intersubband excitations of a bi-dimensional electron gas with the electromagnetic field. This description, based on the electrical dipole gauge, applies to an arbitrary quantum heterostructure embedded in a general multilayered waveguide or a microcavity. We show that the dipole gauge Hamiltonian automatically takes into account the Coulomb interactions in this system. Furthermore, it can be conveniently expressed in terms of the many-body collective plasmon modes, which interact both with each other and with the light field. The dipole gauge therefore provides a suitable framework for the study of solid state Quantum Electrodynamics (QED) phenomena, such as the ultra-strong light-matter interaction regime, occurring at very high electronic densities.

Optical antennas as nanoscale resonators

Recent progress in nanotechnology has enabled us to fabricate sub-wavelength architectures that function as antennas for improving the exchange of optical energy with nanoscale matter. We describe the main features of optical antennas for enhancing quantum emitters and review the designs that increase the spontaneous emission rate by orders of magnitude from the ultraviolet up to the near-infrared spectral range. To further explore how optical antennas may lead to unprecedented regimes of light-matter interactions, we draw a relationship between metal nanoparticles, radio-wave antennas and optical resonators. Our analysis points out how optical antennas may function as nanoscale resonators and how these may offer unique opportunities with respect to state-of-the-art microcavities.

Role of Local Plasmons in Interaction of Light with 1D Periodic Ensembles of Metallic Nanowires

The light propagation through 1D metallic nanowires in strong light–matter interaction regimes have been analyzed theoretically. The theoretical calculations are based on differential formalism using curvilinear coordinate transformation and Fourier modal methods, and its comparison in the case of nanowires with rectangular cross section was performed. The transformation of local plasmon into surface plasmon polariton at an increasing metal filling factor while changing the width of rectangular nanowires was predicted theoretically. The essential enhancement of local plasmon oscillator strength at transformation to surface plasmon polariton was obtained too.

Transition between different coherent light–matter interaction regimes analyzed by phase-resolved pulse propagation

We present phase-resolved pulse propagation measurements that allow us to fully describe the transition between several light-matter interaction regimes. The complete range from linear excitation to the breakdown of the photonic bandgap on to self-induced transmission and self-phase modulation is studied on a high-quality multiple-quantum-well Bragg structure. An improved fast-scanning cross-correlation frequency-resolved optical gating setup is applied to retrieve the pulse phase with an excellent signal-to-noise ratio. Calculations using the semiconductor Maxwell-Bloch equations show qualitative agreement with the experimental findings.

Vacuum Rabi splitting through nonlinear and linear interactions in microcavities

Vacuum Rabi splitting phenomena are discussed in detail based on the semiclassical laser theory. We show that splitting observed in the cavity transmission spectrum gives reciprocal information on the Rabi flopping induced by excited atoms inside a single-resonant-mode cavity. However, for a multi-resonant-mode cavity, observing the transmission peak splitting does not assure the reciprocal Rabi flopping. We also show that temporally oscillatory behavior in transmitted light with pulsed-light-probing, and even the splitting observable in the spontaneous emission spectrum so far reported with planar microcavities, are well explained by spectrum filtering under linear light-matter interaction regimes.

Study of collisionless multiphoton absorption in SF6using picosecond CO2laser pulses

The dynamics of collisionless infrared multiphoton absorption in S${\mathrm{F}}_{6}$ was studied using picosecond C${\mathrm{O}}_{2}$ laser pulses. It was found that at this new regime of light-matter interaction at very high laser intensities, the absorption in the quasicontinuum has a considerable intensity dependence. The deviation from an energy fluence scaling law was found to begin at about 200 MW/${\mathrm{cm}}^{2}$. Above this intensity, the multiphoton interaction between the laser and the molecule should be described by the full coherent Schr\odinger equation rather than by the usual master rate equations. A novel method of preheating the S${\mathrm{F}}_{6}$ molecules is also described and the saturation behavior of these preheated molecules is measured with the picosecond pulses.