An optical metamaterial is a composite in which subwavelength features, rather than the constituent materials, control the macroscopic electromagnetic properties of the material. Recently, properly designed metamaterials have garnered much interest because of their unusual interaction with electromagnetic waves. Whereas nature seems to have limits on the type of materials that exist, newly invented metamaterials are not bound by such constraints. These newly accessible electromagnetic properties make these materials an excellent platform for demonstrating unusual optical phenomena and unique applications such as subwavelength imaging and planar lens design. 'Negative-index materials', as first proposed, required the permittivity, epsilon, and permeability, mu, to be simultaneously less than zero, but such materials face limitations. Here, we demonstrate a comparatively low-loss, three-dimensional, all-semiconductor metamaterial that exhibits negative refraction for all incidence angles in the long-wave infrared region and requires only an anisotropic dielectric function with a single resonance. Using reflection and transmission measurements and a comprehensive model of the material, we demonstrate that our material exhibits negative refraction. This is furthermore confirmed through a straightforward beam optics experiment. This work will influence future metamaterial designs and their incorporation into optical semiconductor devices.
We show a phase-locked array of three quantum cascade lasers with an integrated Talbot cavity at one side of the laser array. The coupling scheme is called diffraction coupling. By controlling the length of Talbot to be a quarter of Talbot distance (Z t /4), in-phase mode operation can be selected. The in-phase operation shows great modal stability under different injection currents, from the threshold current to the full power current. The far-field radiation pattern of the in-phase operation contains three lobes, one central maximum lobe and two side lobes. The interval between adjacent lobes is about 10.5°. The output power is about 1.5 times that of a single-ridge laser. Further studies should be taken to achieve better beam performance and reduce optical losses brought by the integrated Talbot cavity.
Mediated photon-photon interactions are realized in a superconducting coplanar waveguide cavity coupled to a superconducting charge qubit. These nonresonant interactions blockade the transmission of photons through the cavity. This so-called dispersive photon blockade is characterized by measuring the total transmitted power while varying the energy spectrum of the photons incident on the cavity. A staircase with four distinct steps is observed and can be understood in an analogy with electron transport and the Coulomb blockade in quantum dots. This work differs from previous efforts in that the cavity-qubit excitations retain a photonic nature rather than a hybridization of qubit and photon and provides the needed tolerance to disorder for future condensed matter experiments.
Recent progress in superconducting qubits has demonstrated the potential of these devices for the future of quantum information processing. One desirable feature for quantum computing is independent control of qubit interactions as well as qubit energies. We demonstrate a new type of superconducting charge qubit that has a Vshaped energy spectrum and uses quantum interference to provide independent control over the qubit energy and dipole coupling to a superconducting cavity. We demonstrate dynamic access to the strong coupling regime by tuning the coupling strength from less than 200 kHz to more than 40 MHz. This tunable coupling can be used to protect the qubit from cavity-induced relaxation and avoid unwanted qubit-qubit interactions in a multi-qubit system.The electromagnetic coupling between a quantized cavity field and a quantum mechanical two-level system has enabled the understanding of some of the most fundamental interactions between light and matter [1]. Recent progress in this area has been spurred by the advent of circuit quantum electrodynamics (cQED), in which a superconducting qubit is strongly coupled to an on-chip microwave cavity [2]. This architecture can form the backbone of a superconducting quantum computer [3][4][5] and has been used to demonstrate efficient readout [6][7][8][9], complex entangled state preparation [10][11][12][13], and even elementary multi-qubit quantum processors [10,11,14]. However, the same qubit-cavity coupling that enables efficient control and readout also reduces the qubit lifetime [15], and also leads to spurious qubit-qubit crosstalk in a multi-qubit system. To avoid these detrimental effects, it is highly desirable to have dynamic control over the qubit-cavity coupling. Dynamic control has been demonstrated using an external coupling element between two directly coupled phase and flux qubits [16][17][18][19][20][21][22] and between a phase qubit and a lumped element resonator [23]. However, controllable coupling has so far eluded charge qubits such as the transmon because they cannot be coupled using magnetic flux, which is the mechanism employed by the external coupling elements in previous works. We develop a new charge qubit that uses quantum interference to provide an intrinsic method to control the coupling to a coplanar waveguide cavity.This new variety of superconducting charge-based qubit, called the tunable coupling qubit (TCQ), has independent control over the qubit energy and the qubitcavity coupling strength. It is based on a modified transmon design, and hence retains the essential charge noise insensitivity [24]. The quantum interference used to tune the coupling is controlled by applying two small magnetic fluxes with on-chip, fast flux bias lines [14]. In this paper, we start by numerically solving the TCQ Hamiltonian, theoretically modelling the independent tunability of the qubit energy and coupling strength, g. Next, we show that cavity transmission measurements demonstrate a high degree of control over the qubit energy levels and coupling s...
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