arXiv subjects

Shi-Yuan Wang

Publications and source records attributed to Shi-Yuan Wang.

8 recordsLinked to original sources

arXiv2026

Quantum Ring States

Quantum ring states are non-Gaussian mixed states generated by uniformly modulating the phase of one arm of a bipartite Gaussian quantum resource and transmitting the modulated arm through a lossy thermal bosonic channel. For resources such as two-mode squeezed vacuum (TMSV) states and split coherent states, the continuous phase modulation produces classical states that are diagonal in the Fock basis and fully characterized by photon-number distributions involving hypergeometric functions. We precisely characterize how well states obtained with a finite m-ary phase-shift keying (PSK) modulation approximate quantum ring states. We also leverage bounds on hypergeometric functions to develop closed-form and surprisingly tight bounds for information-theoretic quantities involving quantum ring states, such as the von Neumann entropy and the associated Holevo information. We demonstrate the usefulness of quantum ring states by revisiting several canonical problems and deriving new results including: 1) closed-form achievable communication rates with PSK modulation for lossy thermal bosonic channels over a broad range of channel parameters; 2) improved achievable covert throughputs for one-way and round-trip lossy thermal bosonic channels.

quant-ph↗

arXiv2026

Joint Communication and Sensing with Bipartite Entanglement over Bosonic Channels

We consider a joint communication and sensing problem over an optical link in which a low-power transmitter simultaneously communicates with a receiver and identifies the range of a defect producing a backscattered signal. We model the system as a lossy thermal-noise bosonic channel, in which the target location, modeled as a beamsplitter, affects the timing of the backscattered signal. Motivated by the envisioned deployment of entanglement-enabled quantum networks, we allow the transmitter to exploit shared entanglement to assist both sensing and communication. Since entanglement is known to enhance sensing, as demonstrated in Quantum Illumination (QI), and to increase communication rates through entanglement-assisted communication, the transmitter faces a trade-off in allocating its entanglement resources between the two tasks. Our main result is a characterization of these trade-offs in the form of an achievable rate/error-exponent region, which can outperform time-sharing and demonstrates a quantum advantage.

quant-ph↗

arXiv2026

A Quantum-Memory-Free Quantum Secure Direct Communication Protocol Based on Privacy Amplification of Coded Sequences

We develop an information-theoretic analysis of Quantum-Memory-Free (QMF) Quantum Secure Direct Communication (QSDC) under collective attacks as an alternative to the use of a conventional Quantum Key Distribution (QKD) protocol in conjunction with one-time pads. Our main contributions are: 1) a QMF-QSDC protocol that only relies on universal hashing of coded sequences without wiretap coding; 2) a set of privacy amplification theorems for extracting secrecy from coded classical sequences against quantum side-information. These tools open the way to the design of effective QMF-QSDC protocols.

quant-ph↗

arXiv2025

Bounds on Covert Capacity with Sub-Exponential Random Slot Selection

We consider the problem of covert communication with random slot selection over binary-input Discrete Memoryless Channels and Additive White Gaussian Noise channels, in which a transmitter attempts to reliably communicate with a legitimate receiver while simultaneously maintaining covertness with respect to an eavesdropper. Covertness refers to the inability of the eavesdropper to distinguish the transmission of a message from the absence of communication, modeled by the transmission of a fixed channel input. Random slot selection refers to the transmitter's ability to send a codeword in a time slot with known boundaries selected uniformly at random among a predetermined number of slots. Our main contribution is to develop bounds for the information-theoretic limit of communication in this model, called the covert capacity, when the number of time slots scales sub-exponentially with the codeword length. Our upper and lower bounds for the covert capacity are within a multiplicative factor of $\sqrt{2}$ independent of the channel. This result partially fills a characterization gap between the covert capacity without random slot selection and the covert capacity with random selection among an exponential number of slots in the codeword length. Our key technical contributions consist of i) a tight upper bound for the relative entropy characterizing the effect of random slot selection on the covertness constraint in our achievability proof; ii) a careful converse analysis to characterize the maximum allowable weight or power of codewords to meet the covertness constraint. Our results suggest that, unlike the case without random slot selection, the choice of covertness metric does not change the covert capacity in the presence of random slot selection.

cs.IT↗

arXiv2025

Measuring Cosmic Growth Rate with CSST Spectroscopic Survey and Fast Radio Burst

The cosmic growth rate, which is related to peculiar velocity and is a primary scientific objective of galaxy spectroscopic surveys, can be inferred from the Redshift Space Distortion effect and the kinetic Sunyaev-Zel'dovich effect. However, the reconstruction noise power spectrum of the radial velocity field in kSZ is significantly dependent on the measurement of the small-scale galaxy-electron power spectrum $P_{ge}$. In this study, we thoroughly discuss the enhancement of cosmic growth rate measurements facilitated by Fast Radio Bursts, which probe the electron density of the universe along their propagation paths to provide crucial additional information on $P_{ge}$. Subsequently, we utilize future spectroscopic surveys from the Chinese Space Station Telescope and the CMB-S4 experiment, combined with FRB dispersion measures, to achieve precise measurements of the cosmic growth rate at redshifts $z_g = 0.15,0.45,0.75$. Employing Fisher matrix forecasting analysis, we anticipate that constraints on $fσ_8$ will reach a precision of 0.001 with a sample size of $10^6$ FRBs. Furthermore, we perform a global analysis using Markov Chain Monte Carlo methods to constrain key parameters of three distinct dark energy models and a modified gravity model based on cosmic growth rate measurements. The results demonstrate that these refined $fσ_8$ measurements considerably enhance the constraints on relevant cosmological parameters compared to those obtained from Planck. As the number of observed FRBs increases, alongside more precise galaxy surveys and next-generation CMB observations, new opportunities will arise for constraining cosmological models using the kSZ effect and for developing novel cosmological applications of FRBs.

astro-ph.CO↗

arXiv2025

Constraints on Evolutions of Fundamental Constants from Clustering of Fast Radio Burst Dispersion Measure

Constrained measurements of fundamental physical constants using astronomical observational data represent a powerful method for investigating potential new physics. In particular, the dispersion measure (DM) of fast radio bursts (FRBs), which probes the electron density along their propagation paths, may be influenced by the space-time variation of the fine-structure constant $α$. In this study, we analyze the cross-correlation signal between foreground galaxies and the DM of background FRBs to constrain the evolution of $α$. Assuming large-scale structure (LSS) galaxy surveys with the capabilities of the China Space Station Telescope (CSST) at $z=0.15$ and { a mock FRB survey with $N_{\text{FRB}}=10^5$ at $z=0.4$, we test how well $α$ variation can be constrained}, with a standard deviation of $σ(Δα/ α) = 0.0007$ at $z=0.15$. Furthermore, taking into account the nonminimal coupling between the scalar field and the electromagnetic field, the variation in $α$ can lead to the non-conservation of photon number along geodesics. This would result in a violation of the CDDR and affect the evolution of the Cosmic Microwave Background (CMB) temperature. In this work, we { obtain constraints results} on the CDDR parameter $η$ and the parameter $β$ governing CMB temperature evolution at $z=0.15$, yielding $σ(η) = 0.0004$ and $σ(β) = 0.0006$, respectively. Finally, we relate the variation in $α$ to the time evolution of the proton-to-electron mass ratio, { reporting a standard deviation} of $σ(Δμ/μ) = 0.002$ at $z=0.15$. Future FRB surveys hold significant potential for advancing our understanding of the evolution of fundamental physical constants.

astro-ph.CO↗

arXiv2023

Rate and Detection-Error Exponent Tradeoff for Joint Communication and Sensing of Fixed Channel States

We study the information-theoretic limits of joint communication and sensing when the sensing task is modeled as the estimation of a discrete channel state fixed during the transmission of an entire codeword. This setting captures scenarios in which the time scale over which sensing happens is significantly slower than the time scale over which symbol transmission occurs. The tradeoff between communication and sensing then takes the form of a tradeoff region between the rate of reliable communication and the state detection-error exponent. We investigate such tradeoffs for both mono-static and bi-static scenarios, in which the sensing task is performed at the transmitter or receiver, respectively. In the mono-static case, we develop an exact characterization of the tradeoff in open-loop, when the sensing is not used to assist the communication. We also show the strict improvement brought by a closed-loop operation, in which the sensing informs the communication. In the bi-static case, we develop an achievable tradeoff region that highlights the fundamentally different nature of the bi-static scenario. Specifically, the rate of communication plays a key role in the characterization of the tradeoff and we show how joint strategies, which simultaneously estimate message and state, outperform successive strategies, which only estimate the state after decoding the transmitted message.

cs.IT↗

arXiv2021

Covert MIMO Communications under Variational Distance Constraint

The problem of covert communication over Multiple-Input Multiple-Output (MIMO) Additive White Gaussian Noise (AWGN) channels is investigated, in which a transmitter attempts to reliably communicate with a legitimate receiver while avoiding detection by a passive adversary. The covert capacity of the MIMO AWGN is characterized under a variational distance covertness constraint when the MIMO channel matrices are static and known. The characterization of the covert capacity is also extended to a class of channels in which the legitimate channel matrix is known but the adversary's channel matrix is only known up to a rank and a spectral norm constraint.

cs.IT↗