Photon Frequency Research Articles

Highly scalable quantum router with frequency-independent scattering spectra

Abstract Optical quantum routers play a crucial role in quantum networks and have been extensively studied in both theory and experiment, leading to significant advancements in their performance. However, these routers impose stringent requirements for achieving desired routing results, as the incident photon frequency must be in strict resonance with one or several specific frequencies. To address this challenge, we propose an efficient quantum router scheme composed of semi-infinite coupled-resonator waveguide (CRW) and a giant atom. The single-channel router scheme enables stable output with 100% transfer rate over the entire energy band of the CRW. Leveraging this intriguing result, we further propose a multi-channel router scheme that possesses high stability and universality, while also being capable of performing various functionalities. The complete physical explanation of the underlying mechanism for this intriguing result is also presented. We hope that quantum router with output results unaffected by the frequency of the incoming information carriers presents a more reliable solution for the implementation of quantum networks.

Hybrid Boson Sampling

We propose boson sampling from a system of coupled photons and Bose–Einstein condensed atoms placed inside a multi-mode cavity as a simulation process testing the quantum advantage of quantum systems over classical computers. Consider a two-level atomic transition far-detuned from photon frequency. An atom–photon scattering and interatomic collisions provide interactions that create quasiparticles and excite atoms and photons into squeezed entangled states, orthogonal to the atomic condensate and classical field driving the two-level transition, respectively. We find a joint probability distribution of atom and photon numbers within a quasi-equilibrium model via a hafnian of an extended covariance matrix. It shows a sampling statistics that is ♯P-hard for computing, even if only photon numbers are sampled. Merging cavity-QED and quantum-gas technologies into a hybrid boson sampling setup has the potential to overcome the limitations of separate, photon or atom, sampling schemes and reveal quantum advantage.

Broadband photonic frequency measurement based on the frequency-to-carrier phase-shifted mapping and finite extinction ratio

A novel frequency measurement is proposed based on frequency-to-carrier phase-shifted mapping and finite extinction ratio. Due to the frequency dependence of the dispersion phase shift, carrier phase-shifted double-sideband modulation and dispersive effect are combined for effective mapping. Additionally, the finite extinction ratio is introduced to mitigate the influence of unideal parameters on measurement error. To achieve this, a dual-parallel Mach-Zehnder modulator and a dispersion compensating fibre are combined, and a power minimization problem is formulated to establish a mapping table. Theoretical analysis and simulation results show the frequency measurement range over 30 GHz with errors below 180 MHz. Furthermore, the measurement error is reduced below 40 MHz after considering the finite extinction ratio.

Fundamental Laws and Quantum Dynamics

Background: Recently, we obtained a unitary theory of quantum mechanics and general relativity, where a quantum particle is a continuous distribution of matter in the two conjugate spaces of the coordinates and momentum, quantized by the equality of the mass parameter describing the relativistic dynamics of the matter, with the mass as an integral of the matter density. However, in this framework, we have not explicitly revealed the connection between our new theory and the fundamental laws of quantum mechanics. Methods: We analyzed in detail the three fundamental laws of quantum mechanics, explicitly describing experimental data: 1) Planck’s law of the blackbody electromagnetic radiation of a system of electrically charged harmonic oscillators, 2) Einstein’s law of the photon energy proportionality with the photon frequency, and 3) de Broglie’s law of the quantum particle as an oscillator in space. Results: We reobtained the two dynamical equations, in the conjugate spaces of the coordinates and momentum, as functions of the Lagrangian system, unlike the Schrödinger equation, depending on the Hamiltonian. Conclusion: According to the fundamental laws of quantum mechanics, a quantum particle is a continuous distribution of matter with an intrinsic mass, unlike the conventional quantum mechanics for the state occupation probabilities of punctual entities moving with the light velocity and getting an apparent mass only by collisions with some bosons pervading the whole universe. According to these laws, we obtained a quantum theory in agreement with common sense, classical logic, and general relativity.

Light-light scattering in Very Special Relativity Quantum Electrodynamics and cosmic anisotropies

We consider scattering of light by light in Very Special Relativity (VSR) Quantum Electrodynamics (QED) with a non-zero photon mass. In order to preserve gauge invariance and Sim(2) symmetry we made use of a recently introduced infrared regularization of VSR theories. Additionally, we show that all one loop diagrams with any number of photon external legs and zero fermion legs reduce to the standard QED result with the effective electron mass, as required by unitarity. It follows that the Euler-Heisenberg Lagrangian is the same as in QED. The total cross section of scattering of light by light exhibits tiny anisotropies that could be detected at cosmological scales. In particular, they should be looked at the Cosmic Microwave Background (CMB) Radiation for low photon frequencies.

Non-Degenerate Two-Photon Absorption of Fluorescent Protein Chromophores.

Two-photon absorption (2PA), where a pair of photons are absorbed simultaneously, is recognized as a potent bioimaging technique, which depends on the quantified 2PA probability, defined as cross-section (σ2PA). The absorbed photons either have equivalent (ω1 = ω2) or different frequencies (ω1 ≠ ω2), where the former is degenerate 2PA (D-2PA) and the latter is nondegenerate 2PA (ND-2PA). ND-2PA is of particular interest since it is a promising imaging technology with flexibility of photon frequencies and enhanced cross sections, however, it remains a relatively unexplored area compared to D-2PA. This work utilizes time-dependent density functional theory (TD-DFT) and second-order approximate coupled-cluster with the resolution-of-identity approximation (RI-CC2), for the excitation from S0 to S1, to investigate σD-2PA and σND-2PA of FP chromophore models. Interestingly, comparing CAM-B3LYP with the RI-CC2 computations shows qualitative and, in fact, near quantitative agreement in the computed improvements of σND-2PA for comparable (relative) frequency detunings, despite the known underestimations of 2PA cross sections, for TD-DFT results relative to RI-CC2 values. As expected from the 2-state model, the computed values of σND-2PA are quantitatively larger than σD-2PA, where chromophores with the largest values of σD-2PA show greater potential for σND-2PA improvement. Anionic chromophores demonstrated improvements up to 14%, while substantial enhancements were observed in neutral chromophores with some achieving a 30% increase. This work investigates the ND-2PA photophysical characteristics of FP chromophores and identifies qualitative patterns in the computed properties of ND-2PA relative to D-2PA.

A microwave photonic radio frequency memory with tunable delay resolution and Doppler frequency shift

Radar target simulation is essential for radar development. In this paper, a microwave photonic radio frequency memory (RFM) is proposed and experimentally verified. The input radio frequency (RF) signals are delayed and stored in a recirculating loop with a 4-bit binary optical true time delay line (OTTDL), which enables the achievement of the tunable delay resolution and multiple replications. The Doppler frequency shift (DFS) of the delayed signals is achieved by a Mach-Zehnder modulator (MZM) and two cascaded acousto-optic modulators (AOMs), which facilitate a wide tuning range, high precision, and a high spurious suppression ratio (SSR). The experimental results demonstrate that the system has 16 distinct delay resolutions ranging from 0.045 us to 7.576 us. Furthermore, 30 circulations are achieved in the test, indicating that the theoretical maximum storage time is approximately 225 us. Additionally, the frequency shift for 1 GHz–18 GHz RF pulse signals can be tuned over a range of 10 Hz to 10 MHz, with a SSR exceeding 40 dB.

Microwave photonics frequency scanning approach to absolute distance measurement

An absolute distance measurement approach based on microwave photonics is proposed to provide a high-resolution and non-ambiguity range measurement solution by microwave frequency scanning. The microwave interference spectrum containing optical path difference information can be generated through two rounds of intensity modulation. The approach combines the characteristics of easy focusing and collimation of light waves, as well as easy manipulation of microwaves, to achieve accurate absolute distance measurement. The experimental results show that high-precision measurements can be achieved within the frequency scanning range of only 2 GHz. The error of the distance measurement is less than ±0.079 mm. In addition, the effectiveness of the scanning pattern and the data processing algorithm are verified.

Phase-mediated single-photon scattering and nonreciprocal transmission in a coupled resonator waveguide with a three-level giant atom

We theoretically investigate single-photon scattering and nonreciprocal transmission in a coupled resonator waveguide which is coupled to a driven three-level giant atom via two distant sites. In our system, the local coupling phases are introduced to induce intriguing interference effects. As a result, the phase difference can serve as a sensitive controller for the photon scattering. It is found that the photon scattering properties can be effectively tailored by the size of the giant atom, the driving field and the phase difference. Intriguingly, by carefully tuning the parameters such as the atomic dissipation and the phase difference, a perfect nonreciprocal single-photon transmission can be realized. Additionally, the photon frequency can be adjusted by modulating Rabi frequency of the driving field. These results have significant potential for the development of nonreciprocal optical devices using the giant-atom configuration.

Unidirectional self-imaging in multiple shifted photonic crystal interfaces.

In this study, we investigate the unidirectional self-imaging phenomenon in the shifted photonic crystal (PC) heterostructure. A spin-locked topological edge state, which originates from the mismatch of the Wannier center positions, can propagate along the shifted PC interface without backscattering. When the neighboring shifted PC interfaces are close enough, the coupling between the edge states happens, and coupled edge states (CES) can be found. Based on the finite element method (FEM) simulation, the spin-locked multimode interference (MMI) and self-imaging phenomenon of CES, including paired and symmetrical interference, are achieved in multiple shifted PC interfaces. To illustrate the application of the frequency splitters, the T-shaped and double cross-shaped structures with backscattering immunity and spin-locked characteristics are proposed. Our work provides an alternative way toward the design of a topological splitter by utilizing the photonic frequency and spin degrees of freedom at the same time.

Broadband Instantaneous Frequency Measurement Using Frequency-to-Time Mapping and Channelization

A photonic instantaneous microwave frequency measurement scheme based on frequency-to-time mapping and channelization is proposed. An unknown signal is divided into four channels and mixed with a broadband linear frequency-modulated signal. The frequency information is converted to the time domain, and the frequency measurement range has been expanded due to channelization. A simulation system has been constructed to demonstrate the effectiveness of the proposed method. A proof-of-concept experimental result shows that the frequency measurement errors can be kept in 20 MHz with a 10 MHz resolution, and the frequency measurement range is 1 GHz to 39 GHz.

Quantum and coherent signal transmission on a single-frequency channel via the electro-optic serrodyne technique.

Fiber-optical networks are well established to accommodate global data traffic via coherent information transmission. The next generation of telecommunications will require the integration of quantum information into fiber-optic networks, e.g., for quantum key distribution. A promising and scalable route to enable quantum networking is encoding quantum information into the frequency of photons. While the cointegration of frequency-entangled photons with coherent information transmission is achieved via spectral multiplexing, more resource-efficient approaches are required. In this work, we introduce and experimentally demonstrate a transceiver concept that enables the transmission of coherent and frequency-entangled photons over a single-frequency channel. Our concept leverages the serrodyne technique via electro-optic phase modulation leading to very different dynamics for entangled and coherent photons. This enables temporal multiplexing of the respective signals. We demonstrate the preservation of entanglement over the channel in the presence of coherent light. Our approach reveals a strong potential for efficient bandwidth use in hybrid networks.

Radio Images inside Highly Magnetized Jet Funnels Based on Semianalytic GRMHD Models

By performing general-relativistic radiative transfer calculations, we show the radio images of relativistic jets including highly magnetized regions inside jet funnels, based on steady, axisymmetric, and semianalytic general-relativistic magnetohydrodynamics models. It is found that multiple ring images appear at the photon frequency of 230 GHz for nearly pole-on observers, because of the strong light-bending effect on photons generated at the separation surface, which is the boundary between the inflow and outflow flows in the jet funnel. A bright teardrop-shaped component, which extends from the bright rings of the separation surface, also appears in the counterjet region. The diameter of the brightest outermost ring originated from the counterjet is ∼60 μas, which is consistent with the ringlike images of M87 at 86 GHz observed with GMVA, the Atacama Large Millimeter/submillimeter Array, and the Greenland Telescope, whose ring diameter is ∼64−8+4μas . The thinner and smaller-diameter rings are exhibited when the black hole spin magnitude is higher. These morphological features are expected to appear without being prominently affected by the detailed magnetohydrodynamic plasma parameters of our general-relativistic ideal magnetohydrodynamic (GRMHD) jet model, since the location of the separation surface is mainly regulated by the black hole spin. Our GRMHD model and the emission features of the images in the horizon-scale, highly magnetized jet funnel may be tested by future observations, e.g., the next-generation Event Horizon Telescope and the Black Hole Explorer.

Microwave Photonic Frequency Multiplier with Low Phase Noise Based on an Optoelectronic Oscillator

A microwave photonic frequency multiplier with low phase noise based on an optoelectronic oscillator (OEO) is proposed and experimentally demonstrated. In this scheme, a dual-parallel Mach–Zehnder modulator (DPMZM) is employed to generate the third-harmonic frequency of the input radio frequency (RF) signal, while the oscillation frequency of the OEO is also three times the RF signal frequency. By adjusting the bias voltages of different arms in the DPMZM, a triple-frequency signal with a high side-mode suppression ratio of 64.8 dB can be obtained. The experimental results indicate that the output of the frequency-multiplier has a better single-sideband phase noise value, for instance, −126 dBc/Hz@10 kHz at 20.019 GHz. It has improvements of 34 dB and 43.5 dB compared with the input RF signal and the simulated electrical frequency tripler module, respectively.

Insights into the optoelectronic, thermodynamic, and thermoelectric properties of novel BaYCuX3 (X = Se, Te) semiconductors from first-principles investigation

The widely used density functional theory was employed to study an intricate relationship of the optoelectronic, thermodynamic, and transport features of novel quaternary BaYCuX3 (X = Se, Te) semiconductors. The conduction band region is significantly impacted by the Ba-d and Y-d states, with negligible contributions from the S-s/p/d and Te-s/p/d states. The valence and conduction bands peak at the high symmetry Γ and Y sites, revealing an indirect energy band nature. The predicted band gaps for the BaYCuSe3 and BaYCuTe3 using the WC-GGA and TB-mBJ approximations are 0.96, 1.31 eV, and 0.54, 0.89 eV, respectively. The small atomic size of selenium in BaYCuSe3 material contributes to strong bonding, resulting in a larger energy gap as compared to BaYCuTe3. Maximum values of ε1(ω) drop as photon frequency increases, eventually approaching negative in some energy ranges. The absorption coefficient spectra shifted toward lower energy as the anion changed from Se to Te. Furthermore, the BaYCuTe3 has plasmon resonances at higher energies as compared to BaYCuSe3, resulting in increased energy loss. Furthermore, the BaYCuTe3 material exhibits maximum thermal conductivity than BaYCuSe3 across the whole temperature range.

Compact silicon-based Ka-band tunable-phase photonic microwave frequency downconverter.

In this paper, a compact silicon-based photonic microwave frequency downconverter with broadband operation capability and continuous phase shift tunability is proposed and experimentally demonstrated. The photonic converter mainly comprises two micro-ring modulators (MRMs) connected in parallel and a cascaded resonator-based optical bandpass filter (OBPF) whose size is merely 200 × 700 µm2. In the proposed device, a radio frequency (RF) signal and a local oscillator (LO) signal drive the two MRMs for realizing the electro-optic conversion. The OBPF is utilized for selecting the first-order sidebands of both RF and LO signals. By manipulating the phase difference between the RF and LO optical sidebands through thermal-optic effect, the phase of the obtained intermediate frequency (IF) signal from a photodiode can be tuned continuously. Experimental results demonstrate a 137° phase shift while the RF signals of 20 and 40 GHz are downconverted to an IF signal of 0.4 GHz, which indicates the photonic microwave downconverter can be used in the Ka-band phased-array receiver.

Time dilation: A consequence of the speed of light variation

The escape speed from one point-mass M1 is u1 = (−2u1)½ with u1 (= −M1G/s1) the (Newtonian) gravitational potential energy and s1 the distance between M1 and a chosen point. Observing that the escape speed, from two or more masses, increases, the total escape speed (i.e., from all the masses in universe) becomes u = (−2u)½, with u the total potential (energy), which is related, as shown, to the universe mass <mml:math display="inline"> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">u</mml:mi> </mml:mrow> </mml:msub> <mml:mo>.</mml:mo> </mml:math> According to many authors, Mu ≈ 1053 kg, and, on these bases, we found, on Earth, u → c, so we assumed c ≡ u. This equality implies the massiveness of the light, and because of its two related parameters, λ and ν , we inferred that the light has to be composed of longitudinal massive particles, photons (each one having length λ), moving, along rays (succession of photons along the same direction), toward infinity with speed c (function of u), while their frequency ν turns out to be their number, of the same ray, flowing in time unit. These particles, due to their speed and mass, have a momentum, and therefore, if photons and a circling electron should have, at their impact, opposite direction, the electron could fall into its nucleus; hence, the electron should have a different structure, where its charge is not uniformly distributed, whereas it can be considered as a point particle, fixed on the electron surface, facing the atom nucleus during the electron orbits, while the electron charge turns out to be the photons‐electron impact point, where photons are absorbed and released. Due to this electron structure, the incident photons always force the impacting circling electron to move, with a radial velocity w (function of the incident photons frequency) toward wider orbits. On these bases, during these impacts, the electron becomes the source of re-emitted photons; hence, because of the Doppler effect involving both the incident photons and the recoiled electron, the frequency of the re-emitted photons decreases, while their length (due to the electron radial velocity w lasting as long as the interaction time T) increases by the value wT, inducing the invariance of the speed of light, despite any relative motion observer-source; we also found this invariance (which regards the interaction light‐matter only) through the conservation of energy of the incident photons. Regarding the claimed time dilation, which occurs between two atomic clocks (ACs) at different potential u (e.g., at different altitude on Earth), it is shown that any variation Δu implies a variation Δc, and, contemporarily, since the ACs are sources of photons at a given frequency on Earth, Δu gives a variation of the ACs frequency Δν, hence of their ticking time T = 1/ν, and therefore a variation of their counted time. Finally, the equality c = u implies a cosmological reason regarding an endless balance between collapse and dispersion of the universe masses.

Controlling the frequencies of photons emitted by a single quantum dot in a one-dimensional photonic crystal

Subject of study. A single InAs quantum dot in a one-dimensional photonic crystal based on GaAs is examined. Aim of study. The aim of this study is to develop a method for controlling photon emission frequencies from a single quantum dot within a one-dimensional photonic crystal based on changes in the electromagnetic mass of an electron in the photonic crystal medium. Method. The proposed approach leverages the effect of changing the electromagnetic mass of an electron in the photonic crystal medium, manifesting as corrections to electron energy levels depending on the optical density of the medium. To control this density, the injection of free charge carriers and the quadratic electro-optic Kerr effect are proposed. Main results. The feasibility of in situ control of photon emission frequencies from a quantum dot was demonstrated using quantum transitions between the p- and s-states of a hydrogen-like InAs quantum dot situated in the air voids of a one-dimensional GaAs photonic crystal. This control is achieved through the effect of changing the electromagnetic mass of an electron, as well as tuning the refractive index of the photonic crystal via free charge carrier injection and the electro-optic Kerr effect. Calculations indicate that the photon energy control range available in experiments is limited to several tens of microelectronvolts, restricting practical applicability, and the observed displacement effect is smaller than experimentally recorded values. However, the energy level displacement, influenced by the quantum electrodynamic effect under investigation, exhibits a quadratic dependence on the refractive index of the material forming the photonic crystal. Consequently, the method is expected to scale significantly with increasing optical density. Such photonic crystals could be constructed using metamaterials with a high refractive index. Practical significance. The findings of this study, centered on developing a method for controlling photon emission frequencies from a single quantum dot in a one-dimensional photonic crystal, lay the groundwork for photon-emitter interfaces. These interfaces will incorporate key quantum functionalities, including photonic qubits, single-photon light sources, and nonlinear quantum photon-photon gates.

High‐resolution 3D imaging by microwave photonic time division multiplexing‐multiple‐input‐multiple‐output radar with broadband digital beamforming

AbstractA broadband microwave photonic time division multiplexing (TDM) multiple‐input‐multiple‐output (MIMO) radar is proposed in which photonic frequency quadrupling is adopted to generate broadband radar signals and photonic frequency mixing is implemented for de‐chirping processing of radar echoes. By utilising two radio frequency switches to control the signal transmission and reception, TDM‐MIMO mechanism is formed using a single microwave photonic radar transceiver. This microwave photonic TDM‐MIMO radar not only achieves high range resolution using broadband processing but also enables high angular resolution and forward‐looking imaging capability with low system complexity. Besides, a broadband digital beamforming (DBF) method is introduced to solve the broadband beam squint and broadening problems and implement near‐field correction. In the experiment, a microwave photonic TDM‐MIMO radar with an 8×8 T‐shape antenna array is established with a bandwidth of 8 GHz (18–26 GHz) in each channel. The range and angular resolutions are estimated to be ∼2 cm and ∼2°, respectively. Applying the broadband DBF method, high‐resolution 3D imaging of small targets is achieved with good focusing of targets and deep suppression of grating lobes and side lobes. Hence, the proposed microwave photonic TDM‐MIMO radar with broadband DBF provides a promising solution for high‐resolution 3D imaging.

Effective field theories and finite-temperature properties of zero-dimensional superradiant quantum phase transitions

The existence of zero-dimensional superradiant quantum phase transitions seems inconsistent with conventional statistical physics. This work clarifies this apparent inconsistency. We demonstrate the corresponding effective field theories and finite-temperature properties of light-matter interacting systems, and show how this zero-dimensional quantum phase transition occurs. We first focus on the Rabi model, which is a minimum model that hosts a superradiant quantum phase transition. With the path-integral method, we derive the imaginary-time action of the photon degrees of freedom. We also define a dynamical critical exponent as the rescaling between the temperature and the photon frequency, and perform dimensional analysis to the effective action. The dynamical critical exponent shows that the effective theory of the Rabi model is a free scalar field, where a true second-order quantum phase transition emerges. These results are also verified by numerical simulations of imaginary-time correlation functions of the order parameter. Furthermore, we also generalize this method to the Dicke model. Our results make the zero-dimensional superradiant quantum phase transition compatible with conventional statistical physics, and pave the way to understand it in the perspective of effective field theories. Published by the American Physical Society 2024