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Measurement has a special role in quantum theory1: by collapsing the wavefunction it can enable phenomena such as teleportation2 and thereby alter the "arrow of time" that constrains unitary evolution. When integrated in many-body dynamics, measurements can lead to emergent patterns of quantum information in space-time3-10 that go beyond established paradigms for characterizing phases, either in or out of equilibrium11-13. On present-day NISQ processors14, the experimental realization of this physics is challenging due to noise, hardware limitations, and the stochastic nature of quantum measurement. Here we address each of these experimental challenges and investigate measurement-induced quantum information phases on up to 70 superconducting qubits. By leveraging the interchangeability of space and time, we use a duality mapping9,15-17 to avoid mid-circuit measurement and access different manifestations of the underlying phases—from entanglement scaling3,4 to measurement-induced teleportation18—in a unified way. We obtain finite-size signatures of a phase transition with a decoding protocol that correlates the experimental measurement record with classical simulation data. The phases display sharply different sensitivity to noise, which we exploit to turn an inherent hardware limitation into a useful diagnostic. Our work demonstrates an approach to realize measurement-induced physics at scales that are at the limits of current NISQ processors.

We demonstrate a high dynamic range Josephson parametric amplifier (JPA) in which the active nonlinear element is implemented using an array of rf-SQUIDs. The device is matched to the 50 $\Omega$ environment with a Klopfenstein-taper impedance transformer and achieves a bandwidth of 250-300 MHz, with input saturation powers up to -95 dBm at 20 dB gain. A 54-qubit Sycamore processor was used to benchmark these devices, providing a calibration for readout power, an estimate of amplifier added noise, and a platform for comparison against standard impedance matched parametric amplifiers with a single dc-SQUID. We find that the high power rf-SQUID array design has no adverse effect on system noise, readout fidelity, or qubit dephasing, and we estimate an upper bound on amplifier added noise at 1.6 times the quantum limit. Lastly, amplifiers with this design show no degradation in readout fidelity due to gain compression, which can occur in multi-tone multiplexed readout with traditional JPAs., Comment: 10 pages, 10 figures

A low-profile, directive, high-power, simple radio frequency (RF) source can play a crucial role in long-distance communication, sensing, and anti-interference research. Conventional approaches to achieving high-power radiation require a microwave source, an amplifier, and a separate radiating structure. In this article, we transform a static voltage to electromagnetic radiation, which can be electronically steered, using only a thin sheet of metasurface. The proposed approach can be scaled in both power and frequency. The concept makes use of the k = 0 mode in a periodic resonant surface to excite a series of phase-locked individual sources on the surface. The phase-locked sources create an overall coherent mode in the far-field toward the desired direction. The proposed idea is inspired by spark-gap transmitters, pulsed ring-down sources, and antenna arrays to provide a novel and highly scalable electromagnetic source. We envision that the proposed active metasurface for converting a static field to electromagnetic radiation can be potentially used in long-range communication, sensing devices, and radars.

An important measure of the development of quantum computing platforms has been the simulation of increasingly complex physical systems. Prior to fault-tolerant quantum computing, robust error mitigation strategies are necessary to continue this growth. Here, we study physical simulation within the seniority-zero electron pairing subspace, which affords both a computational stepping stone to a fully correlated model, and an opportunity to validate recently introduced ``purification-based'' error-mitigation strategies. We compare the performance of error mitigation based on doubling quantum resources in time (echo verification) or in space (virtual distillation), on up to $20$ qubits of a superconducting qubit quantum processor. We observe a reduction of error by one to two orders of magnitude below less sophisticated techniques (e.g. post-selection); the gain from error mitigation is seen to increase with the system size. Employing these error mitigation strategies enables the implementation of the largest variational algorithm for a correlated chemistry system to-date. Extrapolating performance from these results allows us to estimate minimum requirements for a beyond-classical simulation of electronic structure. We find that, despite the impressive gains from purification-based error mitigation, significant hardware improvements will be required for classically intractable variational chemistry simulations., Comment: 10 pages, 13 page supplementary material, 12 figures. Experimental data available at https://doi.org/10.5281/zenodo.7225821

Different densities of electromagnetic states inside a one dimensional photonic crystal (1D PC) are studied. Hertz vector formalism is used to calculate Green tensor inside a layered structure, semi-analytically. Based on the obtained Green tensor, the local density of electromagnetic states (LDOS) and the density of states (DOS) inside a 1D PC are calculated and discussed. The Green tensor is also used to approximate the density of Bloch states inside the 1D PC and is compared with its exact calculation based on the 1D PC dispersion relations. Using a practical 1D PC parameters in the visible range, the aforementioned quantities are calculated and verified with a full-wave solver based on finite element method (FEM). The formulations and the results are aimed to be helpful in thermal and spontaneous radiation studies.

The density of Bloch modes inside a one dimensional photonic crystal (1D PC) is formulated based on its dispersion relations. This density function has applications in thermal emission inside a 1D PC, as well as controlling the dynamics of active materials embedded in them. After deriving the formulations, a practical 1D PC parameters in the visible range are used to calculate the density of transverse electric and transverse magnetic modes. Compared to the alternative methods such as using Dyadic Greens functions, this method is less complex and is exact. The method applies to any anisotropic medium for which the dispersion equations are available, analytically.

The vast majority of modern microelectronic devices rely on carriers within semiconductors due to their integrability. Therefore, the performance of these devices is limited due to natural semiconductor properties such as band gap and electron velocity. Replacing the semiconductor channel in conventional microelectronic devices with a gas or vacuum channel may scale their speed, wavelength and power beyond what is available today. However, liberating electrons into gas/vacuum in a practical microelectronic device is quite challenging. It often requires heating, applying high voltages, or using lasers with short wavelengths or high powers. Here, we show that the interaction between an engineered resonant surface and a low-power infrared laser can cause enough photoemission via electron tunnelling to implement feasible microelectronic devices such as transistors, switches and modulators. The proposed photoemission-based devices benefit from the advantages of gas-plasma/vacuum electronic devices while preserving the integrability of semiconductor-based devices., Most microelectronic devices today exploit the electronic properties of semiconductors. Here, the authors demonstrate a microelectronic device for free-space electrons by using the enhanced fields in a microstructured metal surface to induce effective photoemission.

We have investigated a magnet-free, nonreciprocal surface wave absorber based on high impedance surfaces (HISs) using a spatial-temporal modulation approach. By controlling embedded switches with a travelling wave, the HIS metasurface is modulated to break the time and spatial symmetry, which enables surface waves to propagate in one direction but be absorbed when propagating in the reverse direction. The nonreciprocity has been demonstrated by an EM-circuit co-simulation. We envision that this could be possibly applied in future communication systems that preferably transmit unidirectionally but absorb interference from the reverse direction caused by reflections or other devices.

High-power microwave (HPM) sources play an important role in applications including RF acceleration, radar, and telecommunications. However, these applications are often limited by weight and the cost. A novel highly scalable two-dimensional high-power microwave source is proposed in this paper. The idea is to first charge the periodic resonating structure with a DC source. Then, using fast high-power switches, the DC source is replaced with a short-circuit leading to an oscillating state in the structure. These oscillations coherently radiate into the far-field, converting the stored DC energy into the desired microwave frequency.

Scattering problems involving wire media are computationally intensive due to the spatially dispersive nature of homogenized wire media. In this work, an integro-differential equation based on a transport formulation is proposed instead of the convolution-form integral equation that directly arises from spatial dispersion. The integro-differential equation is much faster to solve than the convolution equation form, and its effectiveness is confirmed by solving several examples in one-, two-, and three-dimensions. As experimental confirmation of both the integro-differential equation formulation and the homogenized wire medium parameters, several isotropic connected wire medium spheres have been fabricated on a rapid-prototyping machine, and their measured extinction cross sections compared with simulation results. Wire parameters (period and diameter) are varied to the point where homogenization theory breaks down, which is reflected in the measurements.

High-impedance electromagnetic surfaces (HIS) are known for many applications including low-profile antenna design. However, in high power antenna designs using HIS, the air-breakdown between neighboring elements is a limiting factor. We show that the electric field in the gap between neighboring elements is independent of the resonance quality factor of the HIS. Instead, the average electric field inside the HIS cavities (and therefore the stored energy) scales with the resonance quality factor (Q).

Natural and artificial wire materials exhibiting spatial dispersion are considered using a transport (drift-diffusion) model. The connection between drift-diffusion and electron transport in natural materials is highlighted, and then applied to various forms of wire media, leading to the definition of effective conductivity and diffusion parameters that characterize the material. It is shown that the effective material parameters lead to a Debye length that provides a quantitative measure of the strength of spatial dispersion for wire mediums. Further, it is shown that Pekar's additional boundary condition applies in many instances to natural materials as well as artificial wire media, and can be derived from elementary electromagnetics.

Pocklington's integro-differential equation for thin wires with the exact kernel is reformulated using a second derivative formula for improper integrals. This allows for analytical evaluation of the second derivatives, resulting in a pure integral equation, in a similar manner to what is done when using the approximate kernel. However, as opposed to using the approximate kernel, the resulting integral equation developed here is numerically stable even with a simple pulse function/point matching solution. Good convergence for the current is obtained using pulse functions, and the severe unphysical oscillations of the current that are encountered when using pulse functions with the approximate kernel are avoided.

In this work, a novel circuit topology is introduced for the implementation of multiplexers and demultiplexers, called “active distributed (de)multiplexers.” The desired characteristics of active distributed (de)multiplexers as being wideband, planar and active are realized by the proposed microwave circuit. A numerical methodology is presented for its design. An active distributed detriplexer is designed, simulated, fabricated, and measured by the proposed numerical procedure. Computer simulation and measurement results show the effectiveness and suitability of the proposed topology as a detriplexer. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE , 2010. © 2011 Wiley Periodicals, Inc.

The theory of electron emission by metallic photocathodes under the exposure of long wavelength lasers will be studied. Photon energy in long wavelength lasers is less than the work function of the photocathode's material and can only emit electrons via tunneling through the potential barrier. The optical resonance effects (e.g., plasmonic resonances) will be studied as an improvement to the performance of photocathodes. This paper is intended to provide self-sufficient materials to design optical resonant surfaces (e.g., metasurfaces) for electron emission applications.

The electric field properties (distribution and enhancement) of high impedance surfaces under radiation are studied. It is shown that the electric field enhancement at the gap between metal plates has a linear relation with a geometrical factor and is independent of the resonator quality factor. Conditions under which the metasurface can act as an efficient optical absorber are also studied. At the end, wavelengths around 800 nm are suggested for silver (plasmonic) resonators at optical frequencies to maximize the electric field enhancement.

Replacing the electron-hole plasma (solid state) with electron-ion plasma (gas phase) is a completely new approach to design microelectronic devices. Micro-devices with electron-ion plasma, referred to as microplasma devices, can withstand harsh environmental and radiation conditions such as extreme temperatures and damaging electromagnetic pulses (EMP), due to the gas self-healing property.

© 1963-2012 IEEE. The total-internal-reflection (TIR) principle and the concept of an epsilon-near-zero (ENZ) material are combined to form an antenna exhibiting sum and difference patterns with good impedance properties. The ENZ material has been realized using a uniaxial wire medium (WM) metamaterial, and the departure from the behavior of an ideal ENZ material is discussed. The radiation pattern of the fabricated antennas has been measured and compared with simulation results.

A metasurface is proposed to combine DC and laser induced discharges in micro scales. The structure is intended to be used as a platform for a new class of microplasma devices with electro-optical activation.

Receptor coated resonant nanoparticles and quantum dots are proposed to provide a cellular-level resolution image of neural activities inside the brain. The functionalized nanoparticles and quantum dots in this approach will selectively bind to different neurotransmitters in the extra-synaptic regions of neurons. This allows us to detect neural activities in real time by monitoring the nanoparticles and quantum dots optically. Gold nanoparticles (GNPs) with two different geometries (sphere and rod) and quantum dots (QDs) with different sizes were studied along with three different neurotransmitters: dopamine, gamma-Aminobutyric acid (GABA), and glycine. The absorption/emission spectra of GNPs and QDs before and after binding of neurotransmitters and their corresponding receptors are reported. The results using QDs and nanorods with diameter 25nm and aspect rations larger than three were promising for the development of the proposed functional brain mapping approach.

Using a relaxation oscillator circuit, breakdown ($V_{\mathrm{BD}}$) and quench ($V_{\mathrm{Q}}$) voltages of a DC discharge microplasma between two needle probes are measured. High resolution modified Paschen curves are obtained for argon microplasmas including a quench voltage curve representing the voltage at which the plasma turns off. It is shown that, for a point to point microgap (e.g. the microgap between two needle probes) which describes many realistic microdevices, neither Paschen's law applies nor field emission is noticeable. Although normally $V_{\mathrm{BD}}>V_{\mathrm{Q}}$, it is observed that depending on environmental parameters of argon, such as pressure and the driving circuitry, plasma can exist in a different state with equal $V_{\mathrm{BD}}$ and $V_{\mathrm{Q}}$. Using emission line spectroscopy, it is shown that $V_{\mathrm{BD}}$ and $V_{\mathrm{Q}}$ are equal if the atomic excitation by the electric field dipole moment dominantly leads to one of the argon's metastable states ($4P_{5}$ in our study).

Using a realistic quantum master equation we show that the resonance fluorescence spectra of a two-level artificial atom (quantum dot) can be tuned by adjusting its photonic local density of states via biasing of one or more graphene monolayers. The structured photon reservoir is included using a photon Green function theory which fully accounts for the loss and dispersion. The field-driven Mollow triplet spectrum can be actively controlled by the graphene bias in the THz frequency regime. We also consider the effect of a dielectric support environment, and multiple graphene layers, on the emitted fluorescence. Finally, thermal bath effects are considered and shown to be important for low THz frequencies.

Using a realistic quantum master equation we show that the Mollow triplet of a quantum dot can be tuned by adjusting its local density of states via biasing of a graphene monolayer.

Canalization of surface plasmon polaritons (SPPs) on a layer of suspended graphene is investigated. In the canalization regime (Phys. Rev. B. vol. 71, pp. 193105, 2005), spatial harmonics propagate with the same phase velocity. One application of canalization is in sub-wavelength imaging to overcome the diffraction limit. It is shown that a graphene sheet with anisotropic conductivity can provide a canalization regime with the phase velocity of spatial harmonics being equal to the phase velocity in free space. The anisotropic conductivity is derived by tuning the isofrequency contours for SPPs. Similar to the layered perfect lens introduced in (J. Mod. Optics, vol. 50, pp. 1419–1430, 2003), a composite graphene sheet consisting of strips having complex conductivities with alternating positive and negative imaginary parts provides the anisotropic effective conductivity which is essential for canalization.

A transport-based formulation is used to model three-dimensional objects made of a uniaxial wire medium. The resulting drift-diffusion equation is used to calculate the extinction/scattering cross section of various uniaxial wire medium objects. A comparison is made with measurement and full wave simulation results. This method is faster than full wave simulation and provides physical insight into electrodynamic processes within the homogenized medium. The effect of wire period and thickness on the homogenized model is investigated, and a Debye length parameter is used to access the effect of wire length.

A novel geometry is proposed to achieve sum and difference patterns using a monopole antenna as the feed. This geometry consists of a dielectric flare with an embedded uniaxial wire medium acting as an ENZ material. Beams are formed via total internal reflection, but by placing two metallic plates on two side walls of the flare, sum and difference patterns can be interchanged. Physics of the structure are discussed and its radiation pattern, gain and input impedance are calculated by full wave simulation. The antenna is chosen to operate at x band and can be easily fabricated.

The drift-diffusion approach is used to form an integro-differential equation for scattering problems involving three dimensional wire medium objects. The method is applicable to arbitrary three dimensional uniaxial and isotropic geometries. A spherical isotropic wire medium and a cubical uniaxial wire medium object are simulated numerically using the drift-diffusion method. The results are compared with full wave simulation and measurement results.

Summary form only given. The transport model for the wire medium is introduced in (IEEE Trans. on Antennas and Propagation, v. 60, pp. 4219-4239, Sep. 2012) and basically defines an equivalent diffusion parameter (D) and a conductivity (or permittivity) for an isotropic wire medium satisfying the drift diffusion equation Jcond(r, ω)=σ(ω)E(r, ω)-D(ω)∇ρcond(r, ω) in which, Jcond, E, and ρ are homogenized conduction current, electric field, and charge inside the wire medium, respectively. Using this model we have shown previously that scattering problem formulations become simpler and less computationally intensive compared to other real-space methods. The validity of this homogenization method was confirmed for the isotropic wire medium sphere and was compared to the ABC method and the full wave simulation results in previous presentations (URSI 2012 meetings at Boulder and Chicago).

The canalization of terahertz surface plasmon polaritons using a modulated graphene monolayer is investigated for subwavelength imaging. An anisotropic surface conductivity formed by a set of parallel nanoribbons with alternating positive and negative imaginary conductivities is used to realize the canalization regime required for hyperlensing. The ribbons are narrow compared to the wavelength, and are created electronically by gating a graphene layer over a corrugated ground plane. Good quality canalization of surface plasmon polaritons is shown in the terahertz even in the presence of realistic loss in graphene, with relevant implications for subwavelength imaging applications.

The excitation of transverse magnetic (TM) surface plasmons by a point dipole in the vicinity of a multilayered graphene/dielectric system is examined. It was previously shown that the surface plasmon (SP) excited by a vertical dipole on an isolated graphene sheet exhibits a strong excitation peak in the THz region; here we show that, in the presence of a finite-thickness dielectric support layer such as SiO2, considerable spectral content is transferred to a second (perturbed dielectric slab) mode, greatly decreasing and redshifting the excitation peak. The presence of a Si half-space also diminishes the excitation strength, but for graphene on top of SiO2-Si the presence of the SiO2 layer creates a spacer restoring the excitation peak. A two-level quantum emitter is also considered, where it is shown that the addition of a thin dielectric support slab and SiO2-Si geometries affects the spontaneous decay rate in a manner similar to the classical dipole SP excitation peak.

We propose an alternative class of magneto-optical metamaterials offering enhanced angle of rotation in polarization compared to pure magneto-optical materials. In this approach, the permittivity tensor of a magneto-optical material is tailored by embedded wire meshes. We show that the angle of rotation in the magneto-optical metamaterial can be enhanced up to 9 times compared to pure magneto-optical material alone, while the polarization extinction ratio remains below −20dB over more than 2 THz bandwidth and the attenuation coefficient is approximately 1.5dB μm−1.

Electromagnetic absorption and subsequent heating of nanoparticle solutions and simple NaCl ionic solutions is examined for biomedical applications in the radiofrequency range at 13.56 MHz. It is shown via both theory and experiment that for in vitro measurements the shape of the solution container plays a major role in absorption and heating.

A novel microstrip antenna configuration is proposed for the adjustment of its resonance frequency, where grounded metallic strips (as a groove filled with soldering tin or a line of metalized vias) are placed along the rectangular patch edges. The adjustment of the operating frequency may be performed by the gap spacings between the patch and strips. The proposed patch antenna configuration leads to the reduction of its size and also limits the propagation of surface waves on the substrate, which increases the overall radiation efficiency.

In This paper, the method of least square is used for the design and optimization of stepped-impedance low pass filters, which also incorporates impedance matching of source and load impedances. The minimization of the error function is performed by the combination of particle swarm optimization (PSO) and conjugate gradient method (CG). The dispersion relations and step discontinuity equivalent circuits are incorporated in the design procedure. The achieved frequency response of designed filters match those obtained by HFSS simulator software and are much better than those obtained by the classical methods, such as Butterworth, Chebyshev and elliptic filters.

In this paper a novel topology for implementing of active multiplexers and demultiplexers is introduced. This new method is devised based on distributed amplifiers and has unique specifications such as providing possibility of determining gains separately, easy to integrate with other RF devices and small size. In this paper after brief reviewing of distributed amplifiers, we will introduce the proposed topology and its characteristics. To show flexibility of this topology for designing, we will design and optimize a triplexer with unequal input frequency ranges based on the new topology. The optimization method used here is hybrid of conjugate gradient(GC) and genetic algorithm(GA). The result of optimization is confirmed by simulation.

The epsilon-near-zero (ENZ) condition in natural and artificial plasmas is considered for spatially dispersive materials. In the presence of spatial dispersion the ENZ condition must be judged by vanishing of the electric displacement field in real-space. Unlike the simple case of local materials where ENZ occurs at the plasma frequency, in spatially dispersive materials the matter is more complicated. To consider the spatially dispersive case, we obtain the momentum-dependent permittivity in real-space, and define a characteristic length parameter, in addition to the Debye length, which governs polarization screening. Using this formulation, conditions are investigated under which the electric displacement field (equivalently, the real-space permittivity) can vanish or be strongly diminished, even in the presence of spatial dispersion, implementing an ENZ material.

conductivity profile r(x) by finding the electrostatic charge distribution q(x) on the graphene sheet from Laplace’s equation, leading to the chemical potential lcðxÞ and the conductivity via the Kubo formula. It was shown that the ridged structure does indeed allow for the formation of a channel in the vicinity of the ridge for SPP propagation using a single bias, but that the resulting boundary has, as expected, a softened profile (i.e., a soft boundary (SB)) wherein the conductivity is not constant. The work 27 was concerned with the properties of the soft boundary and resulting channel, and the current distribution of the fundamental SPP mode. In this work we consider the various other modes that can propagate along the SB channel, including higher-order modes and edge modes. In particular, we show that unlike the HB case, for a soft boundary the higher-order modes have no apparent low-frequency/long-wavelength cutoff, although as frequency is lowered modal energy tends to spread out laterally along the effectively wider channel. We also show that lowloss edge modes can propagate for which the location where energy is concentrated can be controlled electronically. We then consider two applications of the structure, as a plasmonic voltage-controlled switch and a frequency demultiplexer. Fig. 2 shows the conductivity profile r(x) of the graphene sheet for a representative set of geometrical and FIG. 1. Graphene sheet gated with a ridged, perfect electrically-conducting (PEC) ground plane for the electrostatic bias, forming a soft-boundary graphene nanoribbon. The red area depicts the SPP channel having Im rðxÞ 0 and SPP propagation is prohibited.