Single Quadrature Research Articles

Security analysis of unidimensional continuous-variable quantum key distribution with discretized amplitude modulation

Unidimensional continuous variable quantum key distribution (UD-CVQKD) applies Gaussian modulation on one single quadrature of the coherent state. However, in practical experimentations, the finite resolution of modulator driving voltages will result in Gaussian modulation discretization. To investigate its impact on the security of UD-CVQKD, the discretization of amplitude modulation is modeled and analyzed, with the secret key rate formulated against entangling cloner attack. Simulation results demonstrate that despite the performance degradation, UD-CVQKD protocol with discretized amplitude modulation may relax the restriction on correlation parameters to extend the secure region under certain parameters, which can be beneficial to the practicability of UD-CVQKD.

Performance investigation of multi-aperture digital combining algorithm for satellite-to-ground coherent optical communication

An important component of the future communication network will include satellite-to-ground communication technology. In the meantime, the community of communication network also has a huge capacity as one of its purposes. In this situation, the free-space optical (FSO) communication technology is a potential option for satellite-to-ground communications. A major drawback of FSO communication systems, nevertheless, is atmospheric turbulence. Multi-aperture receiver with digital combining architecture is an effective approach to overcoming the effect of atmospheric turbulence on the performance of free-space optical (FSO) communication. In this paper, a blind digital combining algorithm for coherent FSO communication is proposed. To verify the effectiveness of the proposed combining algorithm, a 10-Gbps data rate single polarization 16-ary quadrature amplitude modulation (SP-16QAM) offline four-aperture simulated turbulence experiment is performed, and the performance of multi-aperture spatial diversity and signal processing is emulated through the experimental data. The results confirm that the proposed blind digital combining algorithm has an excellent performance in average bit error rate (BER). Compared with the single-aperture system, the receiver sensitivity of the four-aperture is increased by 1.2, 4.6, and 6.8 dB for the cases of weak, moderate, and strong turbulence at the SD-FEC threshold, respectively.

Quantum digital signature with unidimensional continuous-variable against the measurement angular error.

The continuous-variable quantum digital signature (CV-QDS) scheme relies on the components of quantum key generation protocol (KGP) to negotiate classical signature, which is more compatible with optical fibers. Nevertheless, the measurement angular error of heterodyne detection or homodyne detection will cause security issues when performing KGP in the distribution stage. For that, we propose to utilize unidimensional modulation in KGP components, which only requires to modulate single quadrature and without the process of basis choice. Numerical simulation results show that the security under collective attack, repudiation attack and forgery attack can be guaranteed. We expect that the unidimensional modulation of KGP components could further simplify the implementation of CV-QDS and circumvent the security issues caused by the measurement angular error.

Radiologic-pathologic correlation of lesions in resected liver specimens with an ex vivo MRI-compatible localization device.

Liver lesion characterization is limited by the lack of an established gold standard for precise correlation of radiologic characteristics with their histologic features. The objective of this study was to demonstrate the feasibility of using an ex vivo MRI-compatible sectioning device for radiologic-pathologic co-localization of lesions in resected liver specimens. In this prospective feasibility study, adults undergoing curative partial hepatectomy from February 2018 to January 2019 were enrolled. Gadoxetic acid was administered intraoperatively prior to hepatic vascular inflow ligation. Liver specimens were stabilized in an MRI-compatible acrylic lesion localization device (27 × 14 × 14 cm3) featuring slicing channels and a silicone gel 3D matrix. High-resolution 3D T1-weighted fast spoiled gradient echo and 3D T2-weighted fast-spin-echo images were acquired using a single channel quadrature head coil. Radiologic lesion coordinates guided pathologic sectioning. A final histopathologic diagnosis was prepared for all lesions. The proportion of successfully co-localized lesions was determined. A total of 57 lesions were identified radiologically and sectioned in liver specimens from 10 participants with liver metastases (n = 8), primary biliary mucinous cystic neoplasm (n = 1), and hepatic adenomatosis (n = 1). Of these, 38 lesions (67%) were < 1 cm. Overall, 52/57 (91%) of radiologically identified lesions were identified pathologically using the device. Of these, 5 lesions (10%) were not initially identified on gross examination but were confirmed histologically using MRI-guided localization. One lesion was identified grossly but not on MRI. We successfully demonstrated the feasibility of a clinical method for image-guided co-localization and histological characterization of liver lesions using an ex vivo MRI-compatible sectioning device. • The ex vivo MRI-compatible sectioning device provides a reliable method for radiologic-pathologic correlation of small (< 1 cm) liver lesions in human liver specimens. • The sectioning method can be feasibly implemented within a clinical practice setting and used in future efforts to study liver lesion characterization. • Intraoperative administration of gadoxetic acid results in enhancement in ex vivo MRI images of liver specimens hours later with excellent image quality.

A Broadband 22–31-GHz Bidirectional Image-Reject Up/Down Converter Module in 28-nm CMOS for 5G Communications

This article presents a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Ka$ </tex-math></inline-formula> -band bidirectional transceiver front end and its integration in an image-reject up/down converter module in 28-nm bulk CMOS. In the radio frequency (RF) front end, a transformer-based transmit/receive (T/R) switch is exploited for minimum area occupation without affecting the linearity and the isolation between the transmitter (TX) and receiver (RX) paths. The TX front end shows 19-dB power gain with an output-referred <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mathrm{ OP}}_{\mathrm{ 1\,dB}}$ </tex-math></inline-formula> of 14 dBm and 18.7% power-added efficiency (PAE). Tested with a 100-MHz 64-QAM orthogonal frequency-division multiplexing (OFDM) modulated input signal, the error vector magnitude (EVM) is below 5% up to an average output power of 6.6 dBm, with a corresponding 7% PAE. The RX in the front end features a minimum noise figure (NF) of 4.9 dB, with 17-dB power gain. The measured input IP3 is –9.2 dBm, while the power consumption is only 35 mW. The RF bandwidth is 22–31 GHz, wide enough to cover the fifth-generation (5G) new radio (NR) bands n257, n258, and n261. The RF front end is also monolithically integrated along with a broadband bidirectional frequency up/down converter, capable of translating the 5G modulated signal from/to a 3-GHz intermediate frequency (IF). The up/down converter is realized with a single bidirectional quadrature mixer shared between the TX and RX paths. At the IF, a single hybrid coupler is used for quadrature phase shifting in upconversion and recombination in downconversion while concurrently keeping the TX and RX IF paths isolated from each other. In the upconversion mode, the module features a 22-dB programmable conversion gain, with a 40-dB minimum in-band image rejection ratio (IRR). The downconversion path shows a 29-dB programmable conversion gain and a minimum measured NF and IRR of 8.5 and 30 dB, respectively, while consuming 110 mW.

Fast Feed-Forward Optical and Electrical Gain Control to Extend the Dynamic Range of the Burst-Mode Digital Coherent Receiver for High-Speed TDM-PON Systems

This paper introduces a new burst-mode coherent receiver configuration that drastically widens the receiver input dynamic range. Its key advance is a fast feed forward gain control scheme for both a semiconductor optical amplifier (SOA) used as a preamplifier and trans-impedance amplifiers (TIAs) set at the coherent receiver. The two-stage optical and electrical gain control greatly decreases the received burst signal's power variations and increases the receiver dynamic range which attenuates the quantization errors in analogue-to-digital conversion (ADC). To elucidate the receiver sensitivity characteristics, bit error rate (BER) calculations are conducted on 10 Gbit/s single polarization quadrature phase shift keying (SP-QPSK) signal coherent reception. The calculations focus on two significant parameters that greatly impact the quantization noise; ADC vertical resolution and received signal's state of polarization (SOP). The calculation results confirm that the proposed configuration achieves high sensitivity, better than −44 dBm, and wide dynamic range of 30 dB in the worst SOP condition, even when 5-bit ADC is used. Transmission experiments verify the calculated sensitivities and extremely high loss budget of 48.6 dB is achieved in 40-km single mode fiber (SMF) transmission. These results show that the proposal has the potential to realize 10 Gbit/s class long-reach and high splitting ratio PONs; the extremely wide dynamic range yields 40 km reach PON systems with 512- or 1024-way splits with no change in receiver configuration.

Absorption and optical selection rules of tunable excitons in biased bilayer graphene

Biased bilayer graphene, with its easily tunable band gap, presents itself as the ideal system to explore the excitonic effect in graphene-based systems. In this paper we study the excitonic optical response of such a system by combining a tight-binding model with the solution of the Bethe-Salpeter equation, the latter being solved in a semianalytical manner, requiring a single numerical quadrature, thus allowing for a transparent calculation. With our approach we start by analytically obtaining the optical selection rules, followed by the computation of the absorption spectrum for the case of a biased bilayer encapsulated in hexagonal boron nitride, a system which has been the subject of a recent experimental study. Excellent agreement is seen when we compare our theoretical prediction with the experimental data.

Accurate Measurement of Human Vital Signs With Linear FMCW Radars Under Proximity Stationary Clutters.

Vital sign detection using linear frequency-modulated continuous-wave (LFMCW) radar may be subject to the proximity stationary clutters. This paper presents a novel technique to synthesize the slow-time I/Q signals, which are equivalent to those in a single tone quadrature CW radar, from a single-channel LFMCW radar. It correlates the two types of radars in such a way that the proximity stationary clutters are translated to direct current (DC) offsets in the synthesized I/Q signals across slow-time. The circle-fitting based DC offsets calibration (DCcal) technique, which was developed for CW radar, can now be applied to eliminate the impact of the proximity stationary clutters in LFMCW radars for accurate vital sign detection. Moreover, the modified differentiate and cross-multiply (MDACM) algorithm can also be leveraged to eliminate the phase ambiguity issue. Thorough theoretical analysis and working principles are presented. Simulations are performed to validate the proposed technique. Moreover, exhaustive experiments are carried out with a millimeter-wave 79 GHz FMCW radar in the office environment. Mechanical vibration and vital signs are extracted with micrometer-level accuracy in the existence of proximity stationary clutters.

Dispersion in doublet-type flows through highly anisotropic porous formations

Steady doublet-type flow takes place in a porous formation, where the log-transform $Y = \ln K$ of the spatially variable hydraulic conductivity $K$ is regarded as a stationary random field of two-point autocorrelation $\rho _Y$ . A passive solute is injected at the source in the porous formation and we aim to quantify the resulting dispersion process between the two lines by means of spatial moments. The latter depend on the distance $\ell$ between the lines, the variance $\sigma ^2_Y$ of $Y$ and the (anisotropy) ratio $\lambda$ between the vertical and the horizontal integral scales of $Y$ . A simple (analytical) solution to this difficult problem is obtained by adopting a few simplifying assumptions: (i) a perturbative solution, which regards $\sigma ^2_Y$ as a small parameter, of the velocity field is sought; (ii) pore-scale dispersion is neglected; and (iii) we deal with a highly anisotropic formation ( $\lambda \lesssim 0.1$ ). We focus on the longitudinal spatial moment, as it is of most importance for the dispersion mechanism. A general expression is derived in terms of a single quadrature, which can be straightforwardly carried out once the shape of $\rho _Y$ is specified. Results permit one to grasp the main features of the dispersion processes as well as to assess the difference with similar mechanisms observed in other non-uniform flows. In particular, the dispersion in a doublet-type flow is observed to be larger than that generated by a single line. This effect is explained by noting that the advective velocity in a doublet, unlike that in source/line flows, is rapidly increasing in the far field owing to the presence there of the singularity. From the standpoint of the applications, it is shown that the solution pertaining to $\lambda \to 0$ (stratified formation) provides an upper bound for the dispersion mechanism. Such a bound can be used as a conservative limit when, in a remediation procedure, one has to select the strength as well as the distance $\ell$ of the doublet. Finally, the present study lends itself as a valuable tool for aquifer tests and to validate more involved numerical codes accounting for complex boundary conditions.

On Solving Problems of Thermal Conductivity on an Anisotropic Plane with a Weakly Permeable Film

The problem of thermal conductivity on an anisotropic plane (x; y) divided into two halfplanes D1(1 &lt; x &lt; 0; y 2 R) and D2(0 &lt; x &lt; 1; y 2 R) by a weakly permeable film x = 0 is considered at given heat sources and a given initial temperature. The anisotropy ellipses are arbitrary (in magnitude and direction) and are the same at all points of the plane. Using the method of convolution of Fourier expansions, the solution of the problem is expressed in single quadratures through the well-known solution of the classical Cauchy problem on an isotropic plane without a film. The results obtained are of practical interest in the problems of heat propagation and conservation in materials with anisotropic properties (crystalline, fibrous materials), in the presence of a thermal insulation film.

Minimization of information leakage in continuous-variable quantum key distribution

A communication protocol based on a Gaussian modulation of squeezed states in a single quadrature and measured via homodyne detection can completely eliminate information leakage to an eavesdropper in a pure-loss channel. However, the asymmetry of the protocol with respect to the quadratures of light presents security issues and the eavesdropper's information is not necessarily minimized for general asymmetric attacks. Here, we perform asymptotic security analysis of the asymmetric protocol against general asymmetric collective attacks and bound the eavesdropper's information via the Heisenberg uncertainty principle. The bound is not tight and therefore, we symmetrize the protocol in a heralding way, discarding the issues of asymmetry altogether. Our proposed heralding protocol asymptotically eliminates information leakage in a pure-loss channel and minimizes leakage in a noisy channel.

Topological error correction with a Gaussian cluster state

Topological error correction provides an effective method to correct errors in quantum computation. It allows quantum computation to be implemented with higher error threshold and high tolerating loss rates. We present a topological a error correction scheme with continuous variables based on an eight-partite Gaussian cluster state. We show that topological quantum correlation between two modes can be protected against a single quadrature phase displacement error occurring on any mode and some of two errors occurring on two modes. More interestingly, some cases of errors occurring on three modes can also be recognised and corrected, which is different from the topological error correction with discrete variables. We show that the final error rate after correction can be further reduced if the modes are subjected to identical errors occurring on all modes with equal probability. The presented results provide a feasible scheme for topological error correction with continuous variables and it can be experimentally demonstrated with a Gaussian cluster state.

Effective screening of medium-assisted van der Waals interactions between embedded particles.

The effect of an implicit medium on dispersive interactions of particle pairs is discussed, and simple expressions for the correction relative to vacuum are derived. We show that a single point Gauss quadrature leads to the intuitive result that the vacuum van der Waals C6-coefficient is screened by the permittivity squared of the environment evaluated near to the resonance frequencies of the interacting particles. This approximation should be particularly relevant if the medium is transparent at these frequencies. In this manuscript, we provide simple models and sets of parameters for commonly used solvents, atoms, and small molecules.

Unidimensional Two-Way Continuous-Variable Quantum Key Distribution Using Coherent States.

We propose a unidimensional two-way continuous-variable quantum key distribution protocol with coherent states, where the sender modulates a single quadrature of the coherent states rather than both quadratures to simplify the structure of a two-way system. Security analysis is performed with a general attack strategy, known as two-mode attack, which helps to reduce limitations in the analysis. The performance of the protocol under all accessible two-mode attacks at fixed distance is illustrated. Further, two typical two-mode attack strategies are obtained from it, which are one-mode attack strategy and optimal two-mode attack strategy. Between them, the one-mode attack is the simplest form of the two-mode attack, while the optimal two-mode attack is the most complicated one. Simulations show that though the system is simplified, the performance of the two-way protocol with unidimensional modulation is still comparable to that of the counterpart with Gaussian modulation even against the optimal two-mode attack when Eve’s ability is maximized. Thus, the proposed protocol simplifies the two-way system while guaranteeing its performance to a certain extent. Especially in a practical system with short transmission distance and high excess noise, the protocol has a good application prospect.

Unconditional mechanical squeezing via backaction-evading measurements and nonoptimal feedback control

Backaction-evading (BAE) measurements of a mechanical resonator, by continuously monitoring a single quadrature of motion, can achieve precision below the zero-point uncertainty. When this happens, the measurement leaves the resonator in a quantum squeezed state. The squeezed state so generated is however conditional on the measurement outcomes, while for most applications it is desirable to have a deterministic, i.e., unconditional, squeezed state with the desired properties. In this work we apply feedback control to achieve deterministic manipulation of mechanical squeezing in an optomechanical system subject to a continuous BAE measurement. We study in details two strategies, direct (Markovian) and state-based (Bayesian) feedback. We show that both are capable to achieve optimal performances, i.e., a vanishing noise added by the feedback loop. Moreover, even when the feedback is restricted to be a time-varying mechanical force (experimentally friendly scenario) and an imperfect BAE regime is considered, the ensuing nonoptimal feedback may still obtain significant amount of squeezing. In particular, we show that Bayesian feedback control is nearly optimal for a wide range of sideband resolution. Our analysis is of direct relevance for ultrasensitive measurements and quantum state engineering in state-of-the-art optomechanical devices.

CLOSED NEWTON-COTES CUBATURE SCHEMES FOR TRIPLE INTEGRALS WITH ERROR ANALYSIS

Most of the problems in applied sciences in engineering contain integrals, not only in one dimension but also in higher dimensions. The complexity of integrands of functions in one variable or higher variables motivates the quadrature and cubature approximations. Much of the work is focused on the literature on single integral quadrature approximations and double integral cubature schemes. On the other hand, the work on triple integral schemes has been quite rarely focused. In this work, we propose the closed Newton-Cotes-type cubature schemes for triple integrals and discuss consequent error analysis of these schemes in terms of the degree of precision and local error terms for the basic form approximations. The results obtained for the proposed triple integral schemes are in line with the patterns observed in single and double integral schemes. The theorems proved in this work on the local error analysis will be a great aid in extending the work towards global error analysis of the schemes in the future.

First Integrals of Differential Operators from SL(2,ℝ) Symmetries

The construction of first integrals for SL(2,R)-invariant nth-order ordinary differential equations is a non-trivial problem due to the nonsolvability of the underlying symmetry algebra sl(2,R). Firstly, we provide for n=2 an explicit expression for two non-constant first integrals through algebraic operations involving the symmetry generators of sl(2,R), and without any kind of integration. Moreover, although there are cases when the two first integrals are functionally independent, it is proved that a second functionally independent first integral arises by a single quadrature. This result is extended for n&gt;2, provided that a solvable structure for an integrable distribution generated by the differential operator associated to the equation and one of the prolonged symmetry generators of sl(2,R) is known. Several examples illustrate the procedures.

Multiple barrier-crossings of an Ornstein-Uhlenbeck diffusion in consecutive periods

We investigate the joint distribution and the multivariate survival functions for the maxima of an Ornstein-Uhlenbeck (OU) process in consecutive time-intervals. A PDE method, alongside an eigenfunction expansion, is adopted with which we first calculate the distribution and the survival functions for the maximum of a homogeneous OU-process in a single interval. By a deterministic time-change and a parameter translation, this result can be extended to an inhomogeneous OU-process. Next, we derive a general formula for the joint distribution and the survival functions for the maxima of a continuous Markov process in consecutive periods. With these results, one can obtain semi-analytical expressions for the joint distribution and the multivariate survival functions for the maxima of an OU-process, with piecewise constant parameter functions, in consecutive time periods. The joint distribution and the survival functions can be evaluated numerically by an iterated quadrature scheme, which can be implemented efficiently by matrix multiplications. Moreover, we show that the computation can be further simplified to the product of single quadratures by imposing a mild condition. Such results may be used for the modeling of heatwaves and related risk management challenges.

Three-body boundary-corrected continuum-intermediate-state method for single charge exchange with the general transition amplitude (1s→nlm) applied to the p–H(1s), α–H(1s), and p–He(1s2) collisions with n≤4

We derive a general quantum-mechanical transition amplitude in the prior version of the three-body boundary-corrected continuum-intermediate-state (BCIS-3B) method for single charge exchange in collisions of heavy nuclei with atomic hydrogenlike targets. The obtained expression is valid for all the transitions from the initial ground to any final hydrogenlike bound states $(1s\ensuremath{\rightarrow}nlm),$ where ${n,l,m}$ is the usual triple of the quantum numbers (principal, angular, magnetic). The outcome is semianalytical: a judicious combination of an analytical calculation (as far as feasible) and the subsequent numerical computations (quadrature for integrals that could not be reduced to closed formulas). The final results for the $T$-matrix elements are a compact double integration computed by numerical quadratures over real variables in finite intervals. The ensuing total cross section is a single numerical quadrature of the squared absolute value of this transition amplitude integrated over the magnitude of the transverse momentum transfer vector. This can provide detailed information on the cross sections for each individual subshell ${n,l,m}$ of the newly formed hydrogenlike atom or ion comprised of a projectile nucleus and the captured electron. Using these general expressions, we computed a large number of state-selective and state-summed cross sections (both differential and total) for electron capture in the $p\text{\ensuremath{-}}\mathrm{H}$, $\ensuremath{\alpha}\text{\ensuremath{-}}\mathrm{H}$, and $p\text{\ensuremath{-}}\mathrm{He}$ collisions at intermediate and high impact energies. The energy dependence of the cross sections for the individual shells and their subshells with the fixed quantum numbers $n$, ${n,l}$, and ${n,l,m}$ are reported via detailed tables and figures. Also, differential cross sections (state selective and summed) are computed for the $p\text{\ensuremath{-}}\mathrm{H}$ collisions at 60, 125, and 5000 keV. All the present results from the BCIS-3B method are found to be in very good agreement with the existing experimental data on differential and total cross sections, both state selective (whenever available) and state summed. The provided cross-section database can find important applications in several investigative fields ranging from plasma physics, astrophysics, and heavy-ion transport physics through fusion research and technology to hadron therapy.

Simple approach for Doppler frequency shift estimation based on a dual-polarization quadrature phase shift keying (DP-QPSK) modulator.

A simple approach to estimating microwave Doppler frequency shift (DFS) based on a single dual-polarization quadrature phase shift keying (DP-QPSK) modulator is proposed and experimentally demonstrated. The scheme is capable of estimating both the value and direction of the DFS simultaneously and precisely owing to the introduction of the reference signal. In the proposed approach, the transmitted signal (microwave carrier) and the reference signal are loaded on the upper branch of the DP-QPSK modulator to generate carrier suppression double-sideband signals, respectively, while the echo signal is loaded on the lower branch of the DP-QPSK modulator to perform carrier suppression single-sideband modulation. Then optical sidebands of two branches are combined and sent to a low-speed photodetector to heterodyne. The value of the DFS is equivalent to the frequency of the beat signal between the transmitted and reference signals; meanwhile, the direction can be distinguished by comparing the frequency of the beat signal between the transmitted and reference signals with the frequency of the beat signal between the echo and reference signals. In the experiment, the accurate measurement of DFSs from $ - {100}\;{\rm kHz}$-100kHz to $ + {100}\;{\rm kHz}$+100kHz at the carrier frequencies of 15, 20, 35, and 39 GHz is implemented with errors less than $ \pm {10}\;{\rm Hz}$±10Hz.