Tootfinder

Super-additivity of quantum capacity in simple channels
Zhen Wu, Qi Zhao, Zhihao Ma
https://arxiv.org/abs/2505.24661 https://arxiv.or…

Super-additivity of quantum capacity in simple channels
The super-additivity of quantum channel capacity is an important feature of quantum information theory different from classical theory, which has been attracting attention. Recently a special channel called ``platypus channel'' exhibits super-additive quantum capacity when combined with qudit erasure channels. Here we consider the ``generalized platypus channel'', prove that it has computable channel capacities, such as both private and classical capacity equal to $1$, and in particular, the ge…

Quantum channel for modeling spin-motion dephasing in Rydberg chains
Christopher Wyenberg, Kent Ueno, Alexandre Cooper
https://arxiv.org/abs/2506.24082 htt…

Quantum channel for modeling spin-motion dephasing in Rydberg chains
We introduce a quantum channel to model the dissipative dynamics resulting from the coupling between spin and motional degrees of freedom in chains of neutral atoms with Rydberg interactions. The quantum channel acts on the reduced spin state obtained under the frozen gas approximation, modulating its elements with time-dependent coefficients. These coefficients can be computed exactly in the perturbative regime, enabling efficient modeling of spin-motion dephasing in systems too large for exac…

Singular value transformation for unknown quantum channels
Ryotaro Niwa, Zane Marius Rossi, Philip Taranto, Mio Murao
https://arxiv.org/abs/2506.24112 http…

Singular value transformation for unknown quantum channels
Given the ability to apply an unknown quantum channel acting on a $d$-dimensional system, we develop a quantum algorithm for transforming its singular values. The spectrum of a quantum channel as a superoperator is naturally tied to its Liouville representation, which is in general non-Hermitian. Our key contribution is an approximate block-encoding scheme for this representation in a Hermitized form, given only black-box access to the channel; this immediately allows us to apply polynomial tra…

Tunable Competing Electronic Orders in Double Quantum Spin Hall Superlattices
Yi-Chun Hung, Chen-Hsuan Hsu, Arun Bansil
https://arxiv.org/abs/2506.22715 ht…

Tunable Competing Electronic Orders in Double Quantum Spin Hall Superlattices
Competing superconducting (SC) and density-wave orders are of key importance in generating unconventional superconductivity and emergent electronic responses. Quasi-one-dimensional models provide insight into these competing orders and suggest higher-dimensional realizations through coupled-wire constructions, but analysis of such systems remains limited. Recent studies suggest that double helical edge states (DHESs) in double quantum spin Hall insulators (DQSHIs) form a two-channel Luttinger l…

Optimizing Mixed Quantum Channels via Projected Gradient Dynamics
Matthew M. Lin, Bing-Ze Lu
https://arxiv.org/abs/2506.21830 https://

Optimizing Mixed Quantum Channels via Projected Gradient Dynamics
Designing a mixed quantum channel is challenging due to the complexity of the transformations and the probabilistic mixtures of more straightforward channels involved. Fully characterizing a quantum channel generally requires preparing a complete set of input states, such as a basis for the state space, and measuring the corresponding output states. In this work, we begin by investigating a single input-output pair using projected gradient dynamics. This approach applies optimization flows cons…

Maximum entropy principle for quantum processes
Siddhartha Das, Ujjwal Sen
https://arxiv.org/abs/2506.24079 https://arxiv.org/pdf/250…

Maximum entropy principle for quantum processes
The maximum entropy principle states that the maximum entropy among all quantum states with a fixed mean energy is achieved only by the thermal state of given mean energy. In this notes, we prove the maximum entropy principle for quantum processes -- the entropy of a quantum channel with fixed mean energy is maximum if and only if the channel is absolutely thermalizing channel with the fixed output thermal state of that mean energy. This allows for an alternate approach to describe emergence of…

Quantum Point Contact with Local Two-body Loss
Kensuke Kakimoto, Shun Uchino
https://arxiv.org/abs/2505.24391 https://arxiv.org/pdf/2…

Quantum Point Contact with Local Two-body Loss
Motivated by recent advances in ultracold atomic gas experiments, we investigate a two-terminal mesoscopic system in which two-body loss occurs locally at the center of a one-dimensional chain. By means of the self-consistent Born approximation in the Keldysh formalism, we uncover mesoscopic current formulas that are experimentally relevant and applicable to the weak dissipation regime. Although these formulas are analogous to those for systems with one-body loss, it turns out that the channel …

Orthogonal Frequency Division Multiplexing Continuous Variable Terahertz Quantum Key Distribution
Mingqi Zhang, Kaveh Delfanazari
https://arxiv.org/abs/2506.22985

Orthogonal Frequency Division Multiplexing Continuous Variable Terahertz Quantum Key Distribution
We propose a novel continuous-variable quantum key distribution (CVQKD) protocol that employs orthogonal frequency-division multiplexing (OFDM) in the terahertz (THz) band to enable high-throughput and secure quantum communication. By encoding quantum information across multiple subcarriers, the protocol enhances spectral efficiency and mitigates channel dispersion and atmospheric attenuation. We present a comprehensive security analysis under collective Gaussian attacks, considering both terre…

An Iterative Methodology for Unitary Quantum Channel Search
Matthew M. Lin, Hao-Wei Huang, Bing-Ze Lu
https://arxiv.org/abs/2506.21455 https://

An Iterative Methodology for Unitary Quantum Channel Search
In this paper, we propose an iterative algorithm using polar decomposition to approximate a channel characterized by a single unitary matrix based on input-output quantum state pairs. In limited data, we state and prove that the optimal solution obtained from our method using one pair with a specific structure will generate an equivalent class, significantly reducing the dimension of the searching space. Furthermore, we prove that the unitary matrices describing the same channel differ by a com…

Quantum thermal state preparation for near-term quantum processors
Jerome Lloyd, Dmitry A. Abanin
https://arxiv.org/abs/2506.21318 https://

Quantum thermal state preparation for near-term quantum processors
Preparation of quantum thermal states of many-body systems is a key computational challenge for quantum processors, with applications in physics, chemistry, and classical optimization. We provide a simple and efficient algorithm for thermal state preparation, combining engineered bath resetting and modulated system-bath coupling to derive a quantum channel approximately satisfying quantum detailed balance relations. We show that the fixed point $\hatσ$ of the channel approximates the Gibbs sta…

Enhanced thermoelectric effects in a driven one-dimensional system
C. X. Zhang, Alessandro Braggio, Alessandro Romito, Fabio Taddei
https://arxiv.org/abs/2506.22329

Enhanced thermoelectric effects in a driven one-dimensional system
We investigate the thermoelectric properties of a one-dimensional quantum system in the presence of an external driving. We employ Floquet scattering theory to calculate linear-response stationary thermoelectric figures of merit in a single-channel conductor subjected to a periodically varying delta-like potential barrier. We include a step barrier in one of the leads as a model of a nanoscale inhomogeneous semiconducting system. In the absence of a step barrier, we found that the external driv…

Family of Multilayer Graphene Superconductors with Tunable Chirality: Momentum-Space Vortices Forged in the Berry-Ring of Fire
Adarsh S. Patri, Marcel Franz
https://arxiv.org/abs/2505.21616

Family of Multilayer Graphene Superconductors with Tunable Chirality: Momentum-Space Vortices Forged in the Berry-Ring of Fire
Recent experiments in rhombohedrally-stacked multilayer graphene heterostructures have reported signatures of chiral superconductivity, emerging from a spin and valley-polarized normal state with broken time-reversal symmetry and an associated anomalous Hall effect. These findings bring into focus the role of the electronic Bloch wavefunction and the quantum geometric tensor in determining the superconducting pairing channel. In this work, we examine superconducting instabilities of a model of …

Reaching the Ultimate Quantum Precision Limit at Colliders: Conditions and Case Studies
Tengyu Ai, Qi Bi, Yuxin He, Jia Liu, Xiao-Ping Wang
https://arxiv.org/abs/2506.10673

Reaching the Ultimate Quantum Precision Limit at Colliders: Conditions and Case Studies
We investigate whether collider experiments can reach the quantum limit of precision, defined by the quantum Fisher information (QFI), using only classical observables such as particle momenta. As a case study, we focus on the $τ^+τ^-$ system and the decay channel $τ\to πν$, which offers maximal spin-analyzing power and renders the decay a projective measurement. We develop a general framework to determine when collider measurements can, in principle, saturate the QFI in an entangled bipar…

This https://arxiv.org/abs/2503.08985 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_csIT_…

Channel Estimation for Rydberg Atomic Receivers
The rapid development of the quantum technology presents huge opportunities for 6G communications. Leveraging the quantum properties of highly excited Rydberg atoms, Rydberg atom-based antennas present distinct advantages, such as high sensitivity, broad frequency range, and compact size, over traditional antennas. To realize efficient precoding, accurate channel state information is essential. However, due to the distinct characteristics of atomic receivers, traditional channel estimation algo…

Thermodynamic criteria for signaling in quantum channels
Yutong Luo, Simon Milz, Felix C. Binder
https://arxiv.org/abs/2506.20428 https://

Thermodynamic criteria for signaling in quantum channels
Signaling quantum channels are fundamental to quantum communication, enabling the transfer of information from input to output states. In contrast, thermalisation erases information about the initial state. This raises a crucial question: How does the thermalising tendency of a quantum channel constrain its signaling power and vice versa? In this work, we address this question by considering three thermodynamic tasks associated with a quantum channel: the generation, preservation, and transmiss…

A digital twin of atomic ensemble quantum memories
Elizabeth Robertson, Benjamin Maa{\ss}, Konrad Tschernig, Janik Wolters
https://arxiv.org/abs/2506.20403

A digital twin of atomic ensemble quantum memories
Accurate performance estimation of experimentally demonstrated quantum memories is key to understand the nuances in their deployment in photonic quantum networks. While several software packages allow for accessible quantum simulation, they often do not account for the loss and noise in physical devices. We present a framework for modeling ensemble-based atomic quantum memories using the quantum channel formalism. We provide a Kraus matrix representation of several experimentally implemented st…

Photoproduction of doubly charmed tetraquark $T_{cc}$ via photon-gluon fusion at ILC and CLIC
Juan-Juan Niu, Hong-Hao Ma
https://arxiv.org/abs/2506.16721 h…

Photoproduction of doubly charmed tetraquark $T_{cc}$ via photon-gluon fusion at ILC and CLIC
The photoproduction of doubly charmed tetraquark $T_{cc}$ is predicted through the resolved channel $γ+g\to \to \langle cc \rangle[n] + \bar{c}+\bar{c} \to T_{cc}+\bar{c}+\bar{c}$ at ILC and CLIC. At $e^{+}e^{-}$ colliders, the initial photons $γ$ can be produced from two primary sources, well-delineated within the $Weiz\ddot{a}cker$ Williams approximation (WWA) and the laser back-scattering (LBS). And the initial gluon can be emitted from the photon. The spin and color quantum number $[n]$ o…

Transportation cost and contraction coefficient for channels on von Neumann algebras
Roy Araiza, Marius Junge, Peixue Wu
https://arxiv.org/abs/2506.04197 h…

Transportation cost and contraction coefficient for channels on von Neumann algebras
We present a noncommutative optimal transport framework for quantum channels acting on von Neumann algebras. Our central object is the Lipschitz cost measure, a transportation-inspired quantity that evaluates the minimal cost required to move between quantum states via a given channel. Accompanying this is the Lipschitz contraction coefficient, which captures how much the channel contracts the Wasserstein-type distance between states. We establish foundational properties of these quantities, in…

Nonstabilizerness and Error Resilience in Noisy Quantum Circuits
Fabian Ballar Trigueros, Jos\'e Antonio Mar\'in Guzm\'an
https://arxiv.org/abs/2506.18976

Nonstabilizerness and Error Resilience in Noisy Quantum Circuits
We investigate how noise impacts nonstabilizerness - a key resource for quantum advantage - in many-body qubit systems. While noise typically degrades quantum resources, we show that amplitude damping, a nonunital channel, can generate or enhance magic, whereas depolarizing noise provably cannot. In an encoding-decoding protocol, we find that, unlike in the coherent case, a sharp decoding fidelity transition does not match a transition in nonstabilizerness. Our results point toward the possibil…

Theory of universal Planckian metal in t-J model: application for high-Tc cuprate superconductors
Yung-Yeh Chang, Khoe Van Nguyen, Kimberly Remund, Chung-Hou Chung
https://arxiv.org/abs/2506.15552

Theory of universal Planckian metal in t-J model: application for high-Tc cuprate superconductors
The mysterious quantum-critical Planckian bad metal phase with perfect T-linear resistivity persisting beyond the quasi-particle limit and universal T-linear scattering rate has been observed in various high-Tc cuprate superconductors. Here, we develop a realistic theoretical approach to this phase in an analytically solvable large-N multi-channel Kondo lattice model, derived from a heavy-fermion formulated conventionaL t-J model, known for qualitatively describing cuprates. This phase is origi…

Exciton-Exciton Annihilation Mediated by Many-Body Coulomb and Phonon Interactions: An Ab Initio Study
Guy Vosco, Sivan Refaely-Abramson
https://arxiv.org/abs/2506.05223

Exciton-Exciton Annihilation Mediated by Many-Body Coulomb and Phonon Interactions: An Ab Initio Study
Exciton-exciton annihilation (EEA), in which two excitons interact to generate high-energy excitations, is an important non-radiative channel in light-induced excited-state relaxation. When efficient, this process offers an alternative route to exciton emission, potentially allowing extended energetically excited particles' lifetime and coherence. These properties are significant in designing and understanding materials-based quantum devices, particularly for low-dimensional semiconductors. Her…

Learning Encodings by Maximizing State Distinguishability: Variational Quantum Error Correction
Nico Meyer, Christopher Mutschler, Andreas Maier, Daniel D. Scherer
https://arxiv.org/abs/2506.11552

Learning Encodings by Maximizing State Distinguishability: Variational Quantum Error Correction
Quantum error correction is crucial for protecting quantum information against decoherence. Traditional codes like the surface code require substantial overhead, making them impractical for near-term, early fault-tolerant devices. We propose a novel objective function for tailoring error correction codes to specific noise structures by maximizing the distinguishability between quantum states after a noise channel, ensuring efficient recovery operations. We formalize this concept with the distin…

A Sagnac-based arbitrary time-bin state encoder for quantum communication applications
Kannan Vijayadharan, Mat\'ias Rub\'en Bola\~nos, Marco Avesani, Giuseppe Vallone, Paolo Villoresi, Costantino Agnesi
https://arxiv.org/abs/2506.08971

A Sagnac-based arbitrary time-bin state encoder for quantum communication applications
Time-bin encoding of quantum information is highly advantageous for long-distance quantum communication protocols over optical fibres due to its inherent robustness in the channel and the possibility of generating high-dimensional quantum states. The most common implementation of time-bin quantum states using unbalanced interferometers presents challenges in terms of stability and flexibility of operation. In particular, a limited number of states can be generated without modifying the optical …

Highly reliable, ultra-wideband, isolator-free quantum-dot mode-locked frequency combs for optical interconnects beyond 3.2Tb/s
Shujie Pan, Victoria Cao, Yiheng Feng, Dingyi Wu, Jie Yan, Junjie Yang, Chao Zhao, Xi Xiao, Siming Chen
https://arxiv.org/abs/2506.02402

Highly reliable, ultra-wideband, isolator-free quantum-dot mode-locked frequency combs for optical interconnects beyond 3.2Tb/s
Quantum dot mode-locked laser-based optical frequency combs are emerging as a critical solution for achieving low-cost, high-efficiency, and large-capacity optical interconnects. The practical implementation of wavelength division multiplexing interconnects necessitates a temperature-stable OFC source with a minimum 100 GHz channel spacing to enable high-bandwidth modulation while mitigating the complexity of optical filtering and detection. By leveraging the advanced co-doping technique and a …

Physics-inspired neural networks as quasi inverse of quantum channels
Sameen Aziz, Muhammad Faryad
https://arxiv.org/abs/2506.11716 https://

Physics-inspired neural networks as quasi inverse of quantum channels
Quantum channels are not invertible in general. A quasi-inverse allows for a partial recovery of the input state, but its analytical results are found only in a restricted space of its parameters. This work explores the potential of neural networks to find the quasi-inverse of qubit channels for any values of the channel parameters while keeping the quasi-inverse as a physically realizable quantum operation. We introduce a physics-inspired loss function based on the mean of the square of the mo…

Radiative decay of $\chi_{c1}$ states in effective Lagrangian approach
Thanat Sangkhakrit, Attaphon Kaewsnod, Ayut Limphirat, Khanchai Khosonthongkee, Warintorn Sreethawong, Nopmanee Supanam, Yupeng Yan
https://arxiv.org/abs/2506.08406

Radiative decay of $χ_{c1}$ states in effective Lagrangian approach
The $χ_{c1}(3872)$ state, first observed by the Belle collaboration with its quantum numbers identified as $J^{PC} = 1^{++}$, has been the subject of extensive research due to its intriguing properties. Several theoretical interpretations have been proposed to explain its unique characteristics, including the $χ_{c1}(2P)$ assignment, a molecular $\bar{D}^{*}D/\bar{D}D^{*}$ configuration, a coupled-channel framework incorporating $c\bar{c}$ and di-meson degrees of freedom, and the compact tetr…

Optimal absorption and emission of itinerant fields into a spin ensemble memory
Linda Greggio, Tristan Lorriaux, Alexandru Petrescu, Mazyar Mirrahimi, Audrey Bienfait
https://arxiv.org/abs/2506.06107

Optimal absorption and emission of itinerant fields into a spin ensemble memory
Quantum memories integrated in a modular quantum processing architecture can rationalize the resources required for quantum computation. This work focuses on spin-based quantum memories, where itinerant electromagnetic fields are stored in large ensembles of effective two-level systems, such as atomic or solid-state spin ensembles, embedded in a cavity. Using a mean-field framework, we model the ensemble as an effective spin communication channel and develop a cascaded quantum model to describe…

Covert Entanglement Generation over Bosonic Channels
Evan J. D. Anderson, Michael S. Bullock, Ohad Kimelfeld, Christopher K. Eyre, Filip Rozp\k{e}dek, Uzi Pereg, Boulat A. Bash
https://arxiv.org/abs/2506.09474

Covert Entanglement Generation over Bosonic Channels
We explore covert entanglement generation over the lossy thermal-noise bosonic channel, which is a quantum-mechanical model of many practical settings, including optical, microwave, and radio-frequency (RF) channels. Covert communication ensures that an adversary is unable to detect the presence of transmissions, which are concealed in channel noise. We show that a $\textit{square root law}$ (SRL) for covert entanglement generation similar to that for classical: $L_{\rm EG}\sqrt{n}$ entangled b…