Photon Research Articles

Simulating photonic devices with noisy optical elements

Quantum computers are inherently affected by noise. While in the long term, error correction codes will account for noise at the cost of increasing physical qubits, in the near term, the performance of any quantum algorithm should be tested and simulated in the presence of noise. As noise acts on the hardware, the classical simulation of a quantum algorithm should not be agnostic on the platform used for the computation. In this paper, we apply the recently proposed noisy gates approach to efficiently simulate noisy optical circuits described in the dual rail framework. The evolution of the state vector is simulated directly, without requiring the mapping to the density matrix framework. Notably, we test the method on both the gate-based and measurement-based quantum computing models, showing that the approach is very versatile. We also evaluate the performance of a photonic variational quantum algorithm to solve the MAX-2-CUT problem. In particular we design and simulate an ansatz, which is resilient to photon losses up to p∼10−3 making it relevant for near-term applications. Published by the American Physical Society 2024

Space radiation measured during first-ever commercial suborbital mission on Virgin Galactic SpaceShipTwo Unity on 29 June 2023

The paper presents the variations of space radiation (primary and secondary galactic cosmic rays (GCR) absorbed dose rate in silicon and flux) measured during the first-ever commercial suborbital flight of the Virgin Galactic (VG) SpaceShipTwo Unity on 29 June 2023. A Portable Dosimeter-Spectrometer Liulin-CNR-VG is used. It is developed in the Space Research and Technology Institute, Bulgarian Academy of Sciences (SRTI-BAS) under a scientific contract with National Research Council of Italy (CNR), Italy. Liulin-CNR-VG size is 63х54 × 23 mm. Its weight is 0.092 kg. During the first part of the SpaceShipTwo flight, up to 14.4 km, the dose rate rises from 0.058 μGy h-1 up to 2.5 μGy h-1. Above the altitude of 30 km, the dose rate falls to 2.2 μGy h-1, while the dose to flux ratio increases to values about 1.0 nGy cm2 particle-1. The latter confirms the outcomes of previous balloon experiments, i.e. the change of the composition of the radiation field of the GCR and secondary radiation source from predominantly light particles as electrons, pions and muons towards heavier particles as protons and neutrons. On the descending part of the flight, one maximum in the flux and dose rate curves is obtained as Regener-Pfotzer maximum (R-PM). The flux calculated by the moving avervage is equal to 1.2 cm-2 s-1 and the dose rate is equal to 2.9 μGy h-1 at an altitude of 13 km. These values are well in line with those expected in conditions of relatively high solar activity, such as during the flight. The dose rates measured by Liulin-CNR-VG are in good agreement with other Liulin data, such as those recorded during balloon flights in 2005 and 2015 and civil aviation flights. The calculated total equivalent dose rate during the VG SpaceShipTwo flight is 7.46 μSv for 1.22 h. This reveals that there is a very small radiation risk for the pilots and astronauts flying at the VG SpaceShipTwo up to 85.1 1 km altitude.

Alleviating Effects of Methyl Jasmonate on Pepper (Capsicum annuum L.) Seedlings under Low-Temperature Combined with Low-Light Stress.

Low temperature combined with low light (LL) is an important factor limiting pepper quality and yield. 'Hang Jiao No. 2' were used as experimental materials, and different concentrations of MeJA (T1 (0 μM), T2 (100 μM), T3 (150 μM), T4 (200 μM), T5 (250 μM) and T6 (300 μM)) were sprayed under LL stress to explore the positive effect of exogenous methyl jasmonate (MeJA) on peppers under LL stress. The photosynthetic properties, osmoregulatory substance, reactive oxygen species, antioxidant enzyme activities, and related gene expressions of the peppers were measured. Our results demonstrated that 200 μM MeJA treatment significantly increased chlorophyll content, light quantum flux per active RC electron transfer (Eto/RC), maximum captured photonic flux per active RC (TRo/RC), energy flux for electron transfer in the excitation cross section (Eto/CSm), energy flux captured by absorption in the excitation cross section (TRo/CSm), soluble protein, and soluble sugar content. Moreover, it significantly improved the maximum photochemical efficiency of PSII (Fv/Fm) and performance index based on absorbed light energy (PI (abs)) by 56.77% and 67.00%, respectively, and significantly decreased malondialdehyde (MDA) content and relative conductivity by 30.55% and 28.17%, respectively. Additionally, antioxidant enzyme activities were elevated, and the expression of the related genes was activated in pepper seedlings under stress, leading to a significant reduction in reactive oxygen species content. In conclusion, our findings confirmed that 200 μM MeJA could reduce the injury of LL to pepper leaves to the photosynthetic organs of pepper leaves, protect the integrity of the cell membrane, and further improve the tolerance of pepper seedlings to LL.

Heralded hyper-CNOT gates for two-photon systems assisted by quantum scattering in waveguides

Photonic hyper-parallel quantum gates play a critical role in high-capacity quantum communication and fast quantum computing. Here, based on photon scattering in one-dimensional (1D) waveguides, we present some heralded schemes for constructing four-qubit hyper-controlled-not (hyper-CNOT) gates in two-photon systems. The qubits are encoded on both the polarization and spatial-mode degrees of freedoms (DOFs) of the photons, which can simplify the quantum circuit and reduce the quantum resource consumption. In our schemes, the faulty scattering events between photons and emitters caused by system imperfections can be filtered out and discarded. That is, our protocols for hyper-CNOT gates work in a heralded way. Our calculations show that, with great progress in the emitter-waveguide systems, our photonic hyper-CNOT gates may be experimentally feasible.

Revealing nonclassicality of multiphoton optical beams via artificial neural networks

The identification of nonclassical features of multiphoton quantum states represents a crucial task in the development of many quantum photonic technologies. Under realistic experimental conditions, a photonic quantum state gets affected by its interaction with several nonideal optoelectronic devices, including those used to guide, detect, or characterize it. The result of such noisy interaction is that the nonclassical features of the original quantum state get considerably reduced or are completely absent in the detected, final state. In this work, the self-learning features of artificial neural networks are exploited to experimentally show that the nonclassicality of multiphoton quantum states can be assessed and fully characterized, even in the cases in which the nonclassical features are concealed by the measuring devices. Our work paves the way toward artificial-intelligence-assisted experimental-setup characterization, as well as quantum state nonclassicality identification. Published by the American Physical Society 2024

Relic density and temperature evolution of a light dark sector

We have developed a set of four fully coupled Boltzmann equations to precisely determine the relic density and temperature of dark matter by including three distinct sectors: dark matter, light scalar, and standard model sectors. The intricacies of heat transfer between dark matter (DM) and the standard model sector through a light scalar particle are explored, inspired by stringent experimental constraints on the scalar-Higgs mixing angle and the DM-scalar coupling. Three distinct sectors emerge prior to DM freeze-out, requiring fully coupled Boltzmann equations to accurately compute relic density. Investigation of forbidden, resonance, and secluded DM scenarios demonstrates significant deviations between established methods and the novel approach with fully coupled Boltzmann equations. Despite increased computational demands, this emphasizes the need for improved precision in relic density calculations, underlining the importance of incorporating these equations in comprehensive analyses. Published by the American Physical Society 2024

Riemannian optimization of photonic quantum circuits in phase and Fock space

We propose a framework to design and optimize generic photonic quantum circuits composed of Gaussian objects (pure and mixed Gaussian states, Gaussian unitaries, Gaussian channels, Gaussian measurements) as well as non-Gaussian effects such as photon-number-resolving measurements. In this framework, we parametrize a phase space representation of Gaussian objects using elements of the symplectic group (or the unitary or orthogonal group in special cases), and then we transform it into the Fock representation using a single linear recurrence relation that computes the Fock amplitudes of any Gaussian object recursively. We also compute the gradient of the Fock amplitudes with respect to phase space parameters by differentiating through the recurrence relation. We can then use Riemannian optimization on the symplectic group to optimize MM-mode Gaussian objects, avoiding the need to commit to particular realizations in terms of fundamental gates. This allows us to “mod out” all the different gate-level implementations of the same circuit, which now can be chosen after the optimization has completed. This can be especially useful when looking to answer general questions, such as bounding the value of a property over a class of states or transformations, or when one would like to worry about hardware constraints separately from the circuit optimization step. Finally, we make our framework extendable to non-Gaussian objects that can be written as linear combinations of Gaussian ones, by explicitly computing the change in global phase when states undergo Gaussian transformations. We implemented all of these methods in the freely available open-source library MrMustard, which we use in three examples to optimize the 216-mode interferometer in Borealis, and 2- and 3-modes circuits (with Fock measurements) to produce cat states and cubic phase states.

SUPER excitation of quantum emitters is a multi-photon process

The swing-up of quantum emitter population (SUPER) scheme allows to populate the excited state of a quantum emitter with near-unity fidelity using two red-detuned laser pulses. Its off-resonant yet fully coherent nature has attracted significant interest in quantum photonics as a valuable tool for preparing single-photon sources in their excited state on demand while simultaneously ensuring straightforward spectral filtering of the laser. However, the physical understanding of this mechanism in terms of energy exchange between the electromagnetic field and the emitter is still lacking. Here, we present a fully quantized model of the swing-up excitation and demonstrate that it is in fact a multi-photon process, where one of the modes loses two or more photons while the other gains at least one. Our findings provide an unexpected physical interpretation of the SUPER scheme and unveil a new non-linear interaction between single emitters and multiple field modes.

Exploring axionlike particle couplings through single top tW -channel and top pair production at the LHC

In this paper, we explore the interactions between light axionlike particles (ALPs) and top quarks, gluons, and W-bosons. Utilizing high-energy probes at the LHC, we probe these couplings in the context of single top quark production associated with a W-boson and an ALP. We analyze the latest LHC Run II data on tt¯ spin correlation measurements to establish constraints on these couplings. Additionally, we compare these constraints with those derived from loop-induced couplings and indirect searches involving B-meson decays. Furthermore, we derive two-dimensional limits on the ALP couplings with top quarks and gluons. Published by the American Physical Society 2024

Design of germanium-silicon diode points to room-temperature future of quantum photonics

A proposed single-photon avalanche diode could enjoy the same performance as current niobium nitride tech without the need for cryogenic temperatures.

Resource-efficient photonic quantum computation with high-dimensional cluster states

Resource-efficient photonic quantum computation with high-dimensional cluster states

Sb2S3/AlGaAs-based reconfigurable metasurface for dynamic polarization and directionality control of quantum emitter emission.

In this article, we report, to the best of our knowledge, for the first time, phase change material (PCM)-based reconfigurable metasurfaces for tailoring different degrees of freedom (DoF) of the quantum emitter (QE) emission, namely polarization and directionality, two key controlling factors in applications such as quantum computing, communication, and chiral optics. We have used a hybrid plasmon-QE coupled bullseye grating system utilizing the unexplored concept of composite nano-antennas in quantum photonics as the basic building block of the structures. Carefully engineered azimuthal width profile of the Sb2S3/AlGaAs composite ridge and selectively controlled transition of PCM (Sb2S3) states provide dynamic control over the amplitude and phase of the scattered radiation. Based on this methodology, we have designed five different metasurfaces for on-demand switching of target DoFs of QE emission, ensuring high collection efficiency due to the near-field coupling scheme. The first two metasurfaces switch the majority of the outgoing radiation from radially polarized to circularly polarized, whereas the next two switch the direction of circularly polarized outgoing radiation by a maximum of 9.23° while maintaining the spin state (or polarization chirality) in the simulation environment. The third metasurface category is capable of on-demand generation and separation of opposite spin states of outgoing radiation by 11.48° utilizing the selectively controlled phase transition of Sb2S3. Such reconfigurable multi-dimensional manipulation of QE radiation has not been investigated previously. This work proves the vast potential of active metasurfaces to modify the DoFs of QE emission, paving the way for high-dimensional quantum sources for high-speed quantum communication, higher dimensional quantum processing, and switchable chiral optics.

Localization–delocalization transition for light particles in turbulence

Small bubbles in fluids rise to the surface due to Archimede's force. Remarkably, in turbulent flows this process is severely hindered by the presence of vortex filaments, which act as moving potential wells, dynamically trapping light particles and bubbles. Quantifying the statistical weights and roles of vortex filaments in turbulence is, however, still an outstanding experimental and computational challenge due to their small scale, fast chaotic motion, and transient nature. Here we show that, under the influence of a modulated oscillatory forcing, the collective bubble behavior switches from a dynamically localized to a delocalized state. Additionally, we find that by varying the forcing frequency and amplitude, a remarkable resonant phenomenon between light particles and small-scale vortex filaments emerges, likening particle behavior to a forced damped oscillator. We discuss how these externally actuated bubbles can be used as a type of microscopic probe to investigate the space-time statistical properties of the smallest turbulence scales, allowing to quantitatively measure physical characteristics of vortex filaments. We develop a superposition model that is in excellent agreement with the simulation data of the particle dynamics which reveals the fraction of localized/delocalized particles as well as characteristics of the potential landscape induced by vortices in turbulence. Our approach paves the way for innovative ways to accurately measure turbulent properties and to the possibility to control light particles and bubble motions in turbulence with potential applications to oceanography, medical imaging, drug/gene delivery, chemical reactions, wastewater treatment, and industrial mixing.

Tailoring polarization in WSe2 quantum emitters through deterministic strain engineering

Quantum emitters in transition metal dichalcogenides (TMDs) have recently emerged as a promising platform for generating single photons for optical quantum information processing. In this work, we present an approach for deterministically controlling the polarization of fabricated quantum emitters in a tungsten diselenide (WSe2) monolayer. We employ novel nanopillar geometries with long and sharp tips to induce a controlled directional strain in the monolayer, and we report on fabricated WSe2 emitters producing single photons with a high degree of polarization (99 ± 4%) and high purity (g(2)(0) = 0.030 ± 0.025). Our work paves the way for the deterministic integration of TMD-based quantum emitters for future photonic quantum technologies.

Deterministic and multiuser quantum teleportation network of continuous-variable polarization states

Quantum teleportation is widely applied as a key ingredient in quantum information science, and quantum network provides unique abilities for upscaling its applications. Polarization state of light is a vital degree of freedom with the advantages of remote transfer and direct light-atom interaction. To construct a multiuser quantum network, deterministic quantum teleportation of polarization state in more users' network remains challenging. Compared with photonic quantum state, the deterministic quantum teleportation network of polarization state is realized with a single set of continuous-variable entangled states. The key techniques include only one set of quadrature entangled network, single quadrature controller, and active polarization controller. Arbitrary polarization state is deterministically and controllably teleported in such a system involving four or three users. This system is deterministic and scalable with user number, which enables the potential application in deterministic metropolitan quantum network. Published by the American Physical Society 2024

Impact of Classical and Quantum Light on Donor-Acceptor-Donor Molecules.

Investigations of entangled and classical two-photon absorption have been carried out for six donor (D)-acceptor (A)-donor (D) compounds containing the dithieno pyrrole (DTP) unit as donor and acceptors with systematically varied electronic properties. Comparing ETPA (quantum) and TPA (classical) results reveals that the ETPA cross section decreases with increasing TPA cross section for molecules with highly off-resonant excited states for single-photon excitation. Theory (TDDFT) results are in semiquantitative agreement with this anticorrelated behavior due to the dependence of the ETPA cross section but not TPA on the two-photon excited state lifetime. The largest cross section is found for a DTP derivative that has a single photon excitation energy closest to resonance with half the two-photon excitation energy. These results are important for the possible use of quantum light for low-intensity energy-conversion applications.

Interpretation of excess in H→Zγ using a light axionlike particle

We interpret the recent excess in a rare decay of the Higgs boson, H→Zγ, using a light axionlike particle (ALP) in the mass range 0.05–0.1 GeV. The dominant decay of such a light ALP is into a pair of collimated photons, whose decay is required to happen before reaching the ECAL detector, such that it mimics a single photon in the detector. It can explain the excess with a coupling CaZHeff/Λ∼4×10−5 GeV−1, while the decay of the ALP before reaching the ECAL requires the diphoton coupling Cγγeff/Λ≥0.35 TeV−1(0.1 GeV/ma)2. A potential test would be the rare decay of the Z boson Z→aH*→a(bb¯) at the Tera-Z option of the future FCC and CEPC. However, it has a branching ratio of only O(10−12), and thus barely testable. The production cross section for pp→Z*→aH via the same coupling CaZHeff/Λ at the LHC is too small for detection. Published by the American Physical Society 2024

Electronic States of Single Perovskite Quantum Dots in Weak and Strong Interaction Regimes: Implications in Electrically Pumped Quantum Emitters.

We investigate the effect of Coulomb interactions on the electronic states of a single perovskite quantum dot (PQD), CsPbBr3, through scanning tunneling microscopy/spectroscopy (STM/S). Under a weak interaction regime, where the time-averaged occupation of electrons in a PQD remains zero, the peaks observed in the differential tunneling conductance (dI/dV) spectrum correspond to the single-particle density of states (DOS) without any electron-electron correlation. However, with a shorter tunnel distance between the STM tip and PQD, additional electrons are trapped in the QD, leading to a strong interaction regime with well-defined electronic fine structures due to the lifting of spin degeneracy in the conduction bands. Interestingly, we observe that the strong Coulomb interaction can modify the spin-orbit coupling (SOC) strength in the PQDs. We have concluded that the energy levels under a strong electron-electron interaction regime are of utmost importance since they will be applicable to electrically pumped PQD-based single photon quantum emitters.

Efficient percolation simulations for lossy photonic fusion networks

The study of percolation phenomena has various applications ranging from social networks or materials science to quantum information. The most common percolation models are bond or site percolation for which the Newman-Ziff algorithm enables an efficient simulation. Here, we consider several nonstandard percolation models that appear in the context of measurement-based photonic quantum computing with so-called graph states and fusion networks. The associated percolation thresholds determine the tolerance to photon loss in such systems and we develop modifications of the Newman-Ziff algorithm to efficiently perform the corresponding percolation simulations. We demonstrate our algorithms by using them to characterize exemplary fusion networks and graph states. Published by the American Physical Society 2024

Perylene-Diimide-Based Supramolecular Radical Anion as a Platform for Highly Effective Photoreduction of Inert Sulfoxide to Sulfide.

Due to the limitations of common photoredox catalysts, unlocking their applications in photoreduction reactions remains an ongoing challenge. We herein present a supramolecular radical anion, PDI(CB[7])2, that formed by the assembly of perylene diimide derivative (PDI) and cucurbit[7]uril (CB[7]) via a host-guest interaction for an effective photoreduction reaction. Studies revealed that it could effectively accomplish a consecutive excitation process by two-photon excitation, enabling a potent photoreductant PDI(CB[7])2• - * that can even reduce the inert feedstocks, such as sulfoxides to sulfides. Mechanistic investigations indicate that, besides exceptional photophysical properties, supramolecular PDI(CB[7])2 also significantly enhances the lifetime and robustness of the in situ generated higher energy photoreductant PDI(CB[7])2• - * upon second quantum photon excitation, leading to the observed highly active photoreducing behavior.