This PDF file contains the front matter associated with SPIE Proceedings Volume 11918.

I will describe our experiments to drive spin and orbital resonance of single diamond nitrogen-vacancy (NV) centers using the gigahertz-frequency strain oscillations produced within a diamond acoustic resonator. Strain-based coupling between a resonator and a defect center takes advantage of intrinsic and reproducible coupling mechanisms while maintaining compatibility with conventional magnetic and optical techniques, thus providing new functionality for quantum-enhanced sensing and quantum information processing. Using a spin-strain interaction at room temperature, we demonstrate coherent spin control and spin coherence protection. At cryogenic temperatures, we use orbital-strain interactions driven by a diamond acoustic resonator to study multi-phonon orbital resonance of a single NV center. Additionally, I’ll describe our efforts to enhance electron-phonon coupling by engineering mechanical resonators with small modal volumes based a semi-confocal acoustic cavity.

The generation and manipulation of quantum states of light has historically played a critical role in the development of quantum information science: from the first violation of Bell’s inequality to the more recent development of near-term quantum algorithms such as the variational quantum eigensolver. In this talk, I present a new frontier for photons at the intersection of quantum mechanics and machine learning. I will first provide a short introduction to the field of quantum photonics, then demonstrate how quantum photonic processors can accelerate both quantum and classical machine learning. Finally, I show how optimization techniques can enhance large-scale quantum control and provide a new path towards efficient verification of near-term quantum processors.

Entanglement and encoding in discrete frequency bins – essentially a quantum analogue of wavelength-division multiplexing – represents a relatively new degree of freedom for quantum information with photons. In this talk I discuss biphoton frequency combs, generated either by spontaneous four-wave mixing (SFWM) from on-chip microring resonators or by spectral filtering of spontaneous parametric down conversion (SPDC) in second order nonlinear crystals. Potential advantages include generation of high dimensional units of quantum information (qudits), which can carry multiple qubits per photon, robust transmission over fiber, and frequency parallelism and routing. Since the initial experiments 2-3 years ago, frequency bin quantum photonics has been advancing rapidly [1, 2]. In this talk I will give special attention to high dimensional entanglement. One of the interesting possibilities is to perform mixing of multiple frequency bins in a single operation, going well beyond nearest neighbor “interactions.” In this vein I will comment on two recent experiments in our lab, each involving more than a dozen frequency bins. One experiment focuses on quantum walks of frequency entangled photon pairs, in which the input state can be coherently steered toward either correlated or anticorrelated quantum walk behavior [3]. In the second case, we show that high-dimensional frequency bin entanglement enables measurement of signal-idler delay at the few picosecond level, ~30× faster than the single photon detectors employed [4].

At the core of most quantum technologies, including quantum networks, quantum computers and quantum simulators, is the development of homogeneous, long lived qubits with excellent optical interfaces, and the development of high efficiency and robust optical interconnects for such qubits. To achieve this goal, we have been studying color centers in diamond (SiV, SnV) and silicon carbide (VSi in 4H SiC), in combination with novel fabrication techniques, and relying on the powerful and fast photonics inverse design approach that we have developed. We illustrate this with a number of demonstrated quantum photonic devices and circuits in diamond and in SiC.

Nonlinear optics, a research area that is emerged after the invention of laser in 1960, continues to be widely explored with a broad range of applications from optical communication and spectroscopy to quantum photonics. A long-standing goal is to realize nonlinear optical structures at progressively low optical power down to quantum regime and electrically-tunable, which is difficult given the small nonlinear coefficients of bulk materials. Currently, there arises a new type of 2D nonlinear optical materials with fascinating properties such as broadband saturable absorption and ultrafast carrier dynamics with a large nonlinear refractive index. Graphene with the ease of fabrication, compatibility with CMOS technology and silicon photonics is a strong contender for a new class of optoelectronic and photonic devices and circuits. In this talk, I will first review graphene’s relevant physics for its application in nonlinear optics complemented by our theoretical work on the quantum treatment of its nonlinear Kerr coefficient. This includes how the Kerr coefficient can be electrically-tuned for device operation as well as new physics of anomalous optical saturation. I will then present our systematic experimental investigation of measuring Kerr coefficient through optical self modulation effect, with an emphasis on its wavelength dependence and temporal evolution via combined z-scan and pump-probe measurements. Finally, I will present our experimental work on ultrafast optical modulation/switching and bistability in a hybrid graphene-silicon photonic crystal nanocavities providing a world-record of modulation/switching speed and depth with the lowest optical power for an integrated nonlinear silicon-based photonic devices.

This talk will describe a technology that enables the utilization of second order nonlinearities, Chi(2) in monolithic semiconductors to be used as an optimal tool box for quantum optics. This approach uses dispersion engineering in Bragg reflection waveguides to harness parametric processes to produce non classical sources through down conversion [1-4]. These can also be realized in conjunction with concomitant dispersion and birefringence engineering in active devices such as semiconductor diode lasers [5-9]. On the classical front, the technology enables novel coherent light sources using frequency conversion in a self pumped chip-form factor. Novel sources for non-classical states of photons in this monolithic platform will be reviewed. These chip-based sources can afford the integration of other devices such as laser pump sources, power and polarization splitters, gates, cavities and much more. This platform essentially offers the capability of transferring current quantum optical setups from the optical table in a lab into a practical realm and even the market place. Also in this talk, some of the application that utilize the aforementioned sources will be discussed, including monolithic photonics architectures that enable deterministic splitting of entangled states of light will be discussed. In addition, sources for target detection and sensing protocols such as quantum illumination in integrated architectures will be also presented. The attributes of this platform offer unique opportunities in metrology applications where size, power, form-factor and space qualification are important factors.

We use entangled photons as the light source in a normal microscope. Using this quantum illumination improves both the resolution and noise rejection in the image. The resolution of any classical imaging system is limited by the diffraction created by the finite size of the imaging lens. By using a light source that emits pairs of entangled photons and carefully controlling a camera that is capable of detecting single photons it is possible to observe these photons arriving two-by-two. Applying camera analysis software to log only these two-by-two events one can form an image from the mid-point (bisector) of each of these pair events. The image formed from the sum of all these bisectors has an improved resolution that surpasses the classical limit. Another advantage of using a quantum illumination is that it allows the two-by-two events from entangled photon pairs to be distinguished from background (classical) light and sensor noise. When processed in this way the resulting image is free of camera noise and any background light may be eliminated. The use of a quantum illumination protocol such as that used here results in the elimination of background light and therefore allows the development of the optical equivalent of quantum radar – a quantum enhanced LIDAR scheme. Using quantum illumination, combined with commercially available cameras that are sensitive to single photons creates a new approach to super-resolution and low noise microscopy. Imaging through noise with quantum illumination, T Gregory, P-A Moreau, E Toninelli, and M J Padgett, Science Advances 6, eaay2652 (2020) Resolution-enhanced quantum imaging by centroid estimation of biphotons, E Toninelli, P-A Moreau, T Gregory, A Mihalyi, M Edgar, N Radwell, and M J Padgett, Optica 6, 347-353 (2019)

Building a quantum computer is not only about having qubits or quantum processors, analogously to classical computers are not only based on transistors or integrated circuits. Accordingly, in the very recent times, a few unique research groups in academia and companies have been exploring and proposing high-level and low-level programming languages, compilers, microarchitecture and instruction set architectures for quantum computation as well as different computer architecture approaches. In other words, developing a quantum computer requires bridging quantum applications and quantum devices. This talk will address the main challenges of building a scalable full-stack quantum computing system followed by a discussion on its architecture focusing on fault tolerance and compilation of quantum algorithms on NISQ devices. I will also provide my vision on how the research community could accelerate the process towards building such a scalable quantum machine, potentially through vertical cross-layer co-design structured methodologies.

The Quanta Image Sensor (QIS) is a photon-counting image sensor conceptualized in 2004 by Fossum and reduced to practice over the past 8 years at Dartmouth using a CMOS image sensor platform, and now referred to as CIS-QIS. This CIS-QIS device is a photon-number resolving sensor that does not use avalanche multiplication, and has been demonstrated in megapixel format with small pixel pitch. This progress will be reported along with associated progress of the spin-out company Gigajot, and other collaborators. In just the past few years, SPAD devices have also been used to explore the QIS concept. Termed SPAD-QIS, the first megapixel SPAD-QIS was reported just in the past few weeks. A comparison of the advantages of CIS-QIS and SPAD-QIS will be presented. Both represent a paradigm shift in image acquisition and may become important for many quantum photonics applications.

III-V compound semiconductor nanowires (NWs) are being developed for the next generation of optoelectronic devices such as photodetectors, photovoltaics, betavoltaics and thermoelectrics. The self-assisted vapor-liquid-solid method is now a well-established technique for the growth of III-V NWs on silicon substrates. In this method, an array of holes in a SiO2 film is used for metal droplet formation, which seeds the growth of vertically oriented NWs within a periodic array. The free lateral surfaces of NWs allow elastic relaxation of lattice misfit strain without the generation of dislocations, permitting unique heterostructures and the direct integration of III-V materials on silicon substrates. Furthermore, NWs permit high optical absorption due to an optical antenna effect. The optical absorption in NW arrays can exceed that due to a thin film of equivalent thickness, enabling high efficiency NW-based photonic devices. Furthermore, optical resonances that depend on the NW diameter allow multispectral absorption. Some of the challenges associated with NW materials and devices, including quantum dot formation, will be illustrated.

Superconducting nanowire single-photon detectors (SNSPDs) have distinguished themselves as a near-optimal choice for a range of quantum information applications, including integrated photonics and quantum key distribution. But the most recent demands from the quantum domain are stretching their capabilities. In particular, photon number resolution has not been readily available in high-performance variants of the devices, and superconducting nanowires were generally thought not to be capable of intrinsic photon number resolution. Recently, significant results in this area have shown that photon number resolution is quite practical with SNSPDs. In addition, wider nanowires have shown good performance, suggesting that the devices can be fabricated using standard photolithography equipment. In this talk, I will review the SNSPD technology, as well as discuss our latest results.

One of the biggest challenges to a viable quantum computer with real-world impact is scaling it up to handle large computations. Continuous-variable (CV) cluster states, which are resource states for measurement-based quantum computation, can be made on a vast scale with minimal experimental resources. I will present recent experimental breakthroughs in producing large-scale CV cluster states, and I will illustrate how to use these states for fault-tolerant quantum computation.

Quantum sensing, quantum networking and communication, and quantum computing have attracted significant attention recently, as these quantum technologies could offer significant advantages over existing technologies. In order to accelerate the commercialization of these quantum technologies, the workforce must be equipped with the necessary skills. We present the results of a qualitative study of the quantum industry, where we conducted a series of interviews with 21 U.S. companies in the quantum industry. The aim of these interviews was to profile the types of jobs that exist and describe the variety of skills valued across the quantum industry. This has allowed us to identify the current routes into the quantum industry, providing a picture of the current role of higher education in training the quantum workforce. Additionally, we enquired about the training and hiring challenges the quantum industry is facing and how higher education may optimize the important role it is currently playing.

The discrete electronic energy levels in atoms and the ability to probe and control them using their interactions with electromagnetic fields have enabled a host of applications in quantum sensing and metrology, including atom-based time and frequency standards, magnetometers, and inertial sensors. Precision measurements with atoms rely on the capability to control the frequency, phase, polarization, and direction of photons used to prepare and measure quantum systems, and thus developments in near-infrared optics and photonics are critical to advancing state-of-the-art atomic sensors. In this talk, I will summarize the basic principles of atom-based quantum sensing and highlight the role of atom-photon interactions in quantum measurements. The benefits and challenges of realizing atom-based quantum sensors will be illustrated through examples from my prior research, including the development of sensitive accelerometers and gyroscopes based on cold-atom interferometers. I will discuss the critical developments in photonic engineering that are still needed to improve the performance and functionality of atom-based-quantum sensors and our research progress at UW-Madison towards addressing these needs.

This presentation will describe Canada’s silicon photonics rapid prototyping consortium, SiEPICfab, and how it can accelerate silicon photonics research and development in quantum information processing. We use electron beam lithography (EBL) to fabricate either individual chips or wafers ranging from 100 mm to 200 mm in size. Fabrication includes waveguides, high-efficiency thermo-optic phase shifters, silicon doping for modulators/heaters/defect-mediated detectors, Bragg grating filters, and NEMS-tunable photonic crystals. Rapid prototyping also allows us to fabricate advanced devices not available in foundries, such as single photon detectors. Finally, successful demonstration of silicon photonic circuits requires testing and packaging - both electrical and optical - and we describe our plans for photonic wire bonding of silicon photonic chips to optical fibres and III-V chips.

Recent advances in materials, control, and nanofabrication now open the prospect for scalable quantum technologies based on solid-state quantum systems. In particular, photonic integrated circuits (PICs) now allow routing photons with high precision and low loss, and solid-state artificial atoms provide high-quality spin-photon interfaces. The first part of this talk will review progress towards quantum memory-integrated PICs for quantum networks and modular quantum computers. The second part of the talk will consider new directions for processing classical and quantum information in deep learning neural networks architectures.

We present recent results from work conducted in the RIT Integrated Photonics Group in collaboration with the Air Force Research Laboratory. We will discuss the generation of high-brightness TM-polarized photon pairs which were generated via nonlinearly coupled resonators. This source produces high quality heralded single photons and provides enhanced tunability to compensate for self-phase modulation and dispersion. Additionally, we will present a two-photon interference experiment using a resonant hong-ou-mandel interferometer, which has a compact footprint when compared to standard Mach-Zehnder interferometers. This new design is capable of high visibility. We conclude with some recent results related to low-loss, high-dimensional packaging for entangled photon applications.

Fibre optics is a mature technology that revolutionized telecommunication. Quantum photonics is an emerging technology still under development. The fusion of the two can bring technologically-robust solutions for quantum applications. Here we give one concrete example of a fiber-optic entangled photon source. Free of alignment, fiber coupling or any birefringence compensating schemes, it is arguably world’s simplest polarization-entangled photon source, and perfectly compatible with the vast fibre-optic network infrastructure. Furthermore, using it to form a fibre-based nonlinear interferometer results in the coupling of the spectral domain with the polarization domain, and tunability in both domains. By manipulating the dispersion and birefringence properties of the linear medium in the interferometer, we experimentally demonstrate altering the biphoton spectrum through biphoton interference, as well as tuning the degree of polarization entanglement. Due to the low-birefringence nature of both the nonlinear and linear media in the interferometer, we can preserve the high-quality polarization entanglement while shaping the biphoton spectrum. Additionally, the coupling of the polarization degree of freedom with the spectral degree of freedom, allowing us to tune the degree of entanglement by simply tuning wavelength. Our fibre-based quantum entanglement sources demonstrate a great deal of flexibility in entanglement engineering for future fibre-optic quantum networks.

Transition-edge sensors (TES’s) are are extremely sensitive calorimeters able to measure energies of the order of a few electronvolts. They are now well-known in the quantum technology community because of their superb combination of high-efficiency— higher than 95% for photons in the near infrared range [1]—essentially zero dark counts, and photon-number resolution. One of the main challenges when working with TES’s is to extract the photon-number information from the continuous output signal of the detectors. The usual procedure is to accumulate signals over some time—typically ~2 GB per minuite—and then use post-processing techniques to obtain photon-number resolution from the recorded signals [2] Here we introduce an FPGA circuit that analyses TES signals in real-time—recording only specific characteristics such as signal area, height, and length—allowing near realtime photon-number resolution and reducing the memory requirements by orders-of-magnitude. Using this new capability, we are able to optimise the number-resolution of the detector to the range we are interested in for each new experiment. In a preliminary study, we calibrated the TES with a weakly-pulsed 820 nm diode laser, and using just the area data from the FPGA were able to discriminate up to 15 photons. We are able to accurately discriminate an n=2 photon Fock state with parts-per-billion precision, dropping to parts-per-hundred precision at n=15 [3]. It is well known that there are physical limits to the precision with which an image can be formed. There are ways in which this limit can be circumvented, for example using super-resolution techniques that exploit the physical structure of the object, or object illumination with entangled states of light. However, in many applications—for example when the object is very far away—we cannot directly interact with the object, or illuminate it with entangled light: the quantum state of the light field is all that is accessible to the observer. Given a finite size imaging system in the far field—i.e., systems with a finite effective numerical aperture—we show the best way to extract the spatial characteristics of the light source. We implement a general imaging method by measuring the complex degree of coherence using linear optics and our photon-number-resolving detectors. In the absence of collective or entanglement-assisted measurements, our method is optimal over a large range of practically relevant values of the complex degree of coherence [4]. We measure the size and position of a small distant source of pseudo-thermal light, and show that our method outperforms the traditional imaging method by an order of magnitude in precision. Additionally, we show that a lack of photon-number resolution in the detectors has only a modest detrimental effect on measurement precision, further highlighting the practicality of this method as a way to gain significant imaging improvements in a wide range of imaging applications. References [1] A. E. Lita, A. J. Miller, and S. W. Nam, Optics Express 16, 3032 (2008). [2] G. Brida, et al., New Journal of Physics 14, 085001, (2012). [3] L. Assis, et al., preprint (2020) [4] L. A. Howard, et al., Physical Review Letters 123, 143604 (2019).

Photons generally weakly interact with each other. While this feature is often useful, for instance, in communication, controllably inducing strong photon-photon interactions is necessary for deterministic, all-optical quantum information processing. Consequently, the weak nonlinearity in optics has historically motivated the use of measurement-based feedback schemes for photonic quantum information processing. Here, we theoretically investigate if coherent photonic quantum information processing could be realized by enhancing weak nonlinearities via Gaussian operations. We find that a Kerr medium with weak material nonlinearity can be engineered to implement a coherent cubic phase gate. Recent progress in developing photonic platforms supporting strong spatial and temporal confinement of pulsed light in low loss and low dispersion nonlinear waveguides could enable an experimental demonstration in the near future.

Quantum photonic devices are emerging from the lab toward real-world applications at an ever increasing pace. The applications range from the secure transfer of information for banking and communication, to quantum radar for national defense, assistance in search and rescue missions, to biomedical applications such as in dose monitoring for cancer treatment as well as in non-invasive imaging of the eye, to diagnose potentially blinding diseases. In these applications, new types of quantum photonic hardware are required including the cutting edge generation of entangled photon pairs and light detection at the single-photon level. In addition to these new types of quantum photonic hardware, manipulation of single photons on a chip is required for photonic quantum computing. In my talk I will discuss how we generate entangled photon pairs with semiconductor quantum dots in shaped nanowire waveguides [1, 2]. I will present our recent work towards engineering these sources to reach perfect entanglement with near-unity efficiency [3, 4, 5]. Currently this is a feat not attainable with leading photon technologies based on parametric down-conversion due to the probabilistic nature of the generation process and self-assembled quantum dots due to dephasing processes and/or poor collection efficiency. I will also present how these quantum light sources can be integrated within a quantum photonic circuit on a silicon chip to route and filter single photons [6, 7]. Further to this, I will present our newest and most exciting work. We have developed a new type of quantum sensor that detects light over an unprecedented wavelength range, from the UV to near-infrared with high speed and timing resolution [8]. Lastly, I will illuminate how our nanostructure is uniquely shaped to achieve near-unity efficiency over the entire wavelength range, and show how we can extend the wavelength detection range to the infrared and beyond in the future, to continue changing the future of quantum photonic devices from the lab to the real world. [1] M.A.M. Versteegh et al., Observation of strongly entangled photon pairs from a nanowire quantum dot, Nature Commun. 5, 5298 (2014). [2] K.D. Jöns et al., Bright nanoscale source of deterministic entangled photon pairs violating Bell’s inequality, Scientific Reports 7, 1700 (2017). [3] A. Fognini et al., Dephasing free photon entanglement with a quantum dot, ACS Photonics 6 (7), 1656-1663 (2019). [4] A. Fognini et al., Universal fine-structure eraser for quantum dots, Optics Express 26 (19), 24487-22496 (2018). [5] M. Zeeshan et al., Proposed scheme to generate bright entangled photon pairs by application of a quadrupole field to a single quantum dot, Phys. Rev. Lett. 122, 227401 (2019). [6] I.E. Zadeh et al., Deterministic integration of single photon sources in silicon based photonic circuits, Nano Lett. 16 (4), 2289-2294 (2016). [7] A. Elshaari et al., On-chip single photon filtering and multiplexing in hybrid quantum photonic circuits, Nature Commun. 8, 379 (2017). [8] S. Gibson et al., Nature Nanotechnology 14 (5), 473 (2019).

Quantum Radar! Check out what Wikipedia says about it: it might render stealth aircraft obsolete. Watch YouTube videos that purport to explain all about it. Read press reports in which China claims it field tested one in 2016. But is there any fire underneath all that smoke? This talk will answer that question by telling the story of “quantum illumination”, from its beginnings through recent theoretical and experimental results. Quantum illumination is the only quantum radar concept that has been proven, theoretically, to outperform all classical radars of the same transmitted energy in detecting a weakly-reflecting target that is embedded in strong background noise. It uses a source of quadrature-entangled signal and idler beams to gain its target-detection performance improvement despite loss and noise that destroys the entanglement. A realistic assessment of that improvement's utility, however, shows that its value is severely limited. Nevertheless, the fact that entanglement can be of value on an entanglement-breaking channel — the meta-lesson of the quantum illumination story — should spur continued research on quantum radar.

Quantum information processing and quantum communication are novel protocols that originate from the very fundamental and philosophical questions on superposition and entanglement raised since the early days of quantum mechanics. Strikingly, these new protocols offer capabilities beyond communication task possible with classical physics. One very important example is the secure key exchange based on the transmission of individual quantum signals between communication partners. The big vision and frontier in the field of quantum communication research is the development of a Quantum Internet, which establishes entanglement between many different users and devices. Extending today’s internet, the Quantum Internet will readily transfer quantum bits, rather than classical bits, between users near and far and over multiple different channels and could be used for secure communications, quantum computer networks and metrological applications. I will discuss recent advances on implementations and tools useful for generating and distributing photonic quantum entanglement over robust channels including. Time-bin encoding and reference-frame-free protocols. I will also present an overview of the upcoming Canadian quantum communication satellite QEYSSAT.

Recent achievements in the area of integrated quantum optics and quantum information processing have shown impressive progress for the implementation of linear circuits based on monolithic waveguide structures. Most experiments are based on χ(3) -media, such as glas, silicon-on insulator or silica-on-silicon. In these platforms the implementation of highly efficient sources, frequency converters and fast active phase shifters and modulators pose severe challenges. The use of advanced waveguides structures, which harness a χ(2) –non-linearity, allows for the realization various devices with multiple functionalities. These include single- and multi-channel sources with high brightness, quantum frequency conversion with tailored spectral-temporal properties, and circuits comprising degenerate pair generation in orthogonal polarization, linear elements, and active elements such as polarization rotators or an electro-optically controllable time delay. Here we present our latest progress for the implementation of integrated devices based on χ(2) –media for quantum circuits and quantum communication systems.

In this talk we will discuss how entanglement is defined with respect to separability, and how the strategies for quantifying two-party entanglement can be extended to multiple parties. Though residual entanglement (i.e., what is left when two-party entanglement is subtracted away) is a popular concept for measuring three-party entanglement, we criticize this and expand on a new resource-based measure known as the tri-partite entanglement of formation. Though there remain multiple fundamental questions to be answered on measures of multi-partite entanglement, we show how the tri-partite entanglement of formation can be bounded from below using experimental correlations in much the same way as was done for two parties. Moreover, we give examples showing how much tripartite entanglement may be present in entangled photon triplets generated in nonlinear optics, and provide a general witness for N-partite entanglement. In our development of the N-partite witness, we also discovered something interesting about the nature of quantum correlations. Though there is no quantum-imposed limit to the correlations two parties can share (e.g., in both position and in momentum), there is such a limit for three or more parties.

I will present an overview of the newly-created NSF Quantum Leap Challenge Institute for enhanced sensing and distribution using correlated quantum states. Under the leadership of director Jun Ye, our multi-institutional center will collaborate to explore how advanced quantum sensing can discover new fundamental physics, develop and apply novel quantum technologies, provide tools for a national infrastructure in quantum sensing, and train a quantum savvy workforce.

Babak Saif (NASA), Carl Williams (NIST), and Dominique Dagenais (NSF) and moderator, Don Figer, will discuss the status of quantum research programs in their government agencies and plans over the next year.

Jody Burks (IBM), Shreya Prasanna Kumar (Xanadu), Susan Mniszewski (LANL), Eleanor Rieffel (NASA) and Ying Ju Wang (Cold Quanta) will discuss increasing the outreach efforts for diversity in quantum and creating a community among women in quantum research with moderator Sonia Lopez Alarcon.

From all types of plasmonic and photonics nanostructures developed for room-temperature single-photon source applications the highest Purcell factor with increasing emitter radiative decay rate and enhancement in the total fluorescence intensity were obtained with metal plasmonic patch (gap) nanoantennas. We report on sporadic appearance of ultrabright intensity spikes (up to ~400─900 kcounts/s) in time traces of photoluminescence from 100-nm silver nanocubes (widely used in patch plasmonic nanoantennas) under 532 or 633 nm laser excitation. Possible mechanisms of spikes are discussed.

We present an analytical calculation of plasmon excitation in a 2D conducting material by a thin horizontally arranged polarized cylindrical tip. This minimalistic model is used as a core for simulation of scattering type surface near-field microscopy (s-SNOM) of 2D materials. Due to its simplicity, it provides better understanding of s-SNOM operation and measurements it's able to perform.

We describe an architecture for fault-tolerant universal quantum computation suited for donor qubits in silicon, coupled by photonic interconnects. The required quantum primitives are local measurements/unitaries, and a non-local Pauli measurement.

We investigate the temperature dependence of valley polarization in WS2 heterostructures. WS2 layer is considered as an optically active material. The influence of heterostructures of different materials on the degree of valley polarization is depicted. The results indicate that unlike interaction in WS2 encapsulated with hBN, the interaction between WS2 and graphene has an intense impact on the temperature dependence depolarization. Furthermore, intervalley scattering rates under resonant and non-resonant excitation energy as the crucial parameters to see the temperature dependence by considering Fröhlich coupling are calculated. The results show the scattering rate is almost independent of temperature due to large phonon energy. Subsequently, the major contribution of observed valley depolarization should come from the change in the radiative lifetime.

Due to their compatibility to existing telecom technology, continuous variable (CV) weak coherent state protocols are promising candidates for a broad deployment of quantum key distribution (QKD) technology. We demonstrate how an existing simulation framework for modelling classical optical systems can be utilized for simulations of weak-coherent CV-QKD links. Having complemented the physical simulation layer by the post-processing layer (reconciliation and privacy amplification), we are able to estimate secure key rates from simulations, greatly boosting the development speed of practical CV-QKD schemes and implementations.