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Transformations in quantum networks via local operations assisted by finitely many rounds of classical communication Quantum (IF 6.4) Pub Date : 2024-03-14 Cornelia Spee, Tristan Kraft
Recent advances have led towards first prototypes of quantum networks in which entanglement is distributed by sources producing bipartite entangled states. This raises the question of which states can be generated in quantum networks based on bipartite sources using local operations and classical communication. In this work, we study state transformations under finite rounds of local operations and
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Can Error Mitigation Improve Trainability of Noisy Variational Quantum Algorithms? Quantum (IF 6.4) Pub Date : 2024-03-14 Samson Wang, Piotr Czarnik, Andrew Arrasmith, M. Cerezo, Lukasz Cincio, Patrick J. Coles
Variational Quantum Algorithms (VQAs) are often viewed as the best hope for near-term quantum advantage. However, recent studies have shown that noise can severely limit the trainability of VQAs, e.g., by exponentially flattening the cost landscape and suppressing the magnitudes of cost gradients. Error Mitigation (EM) shows promise in reducing the impact of noise on near-term devices. Thus, it is
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Teleportation of Post-Selected Quantum States Quantum (IF 6.4) Pub Date : 2024-03-14 Daniel Collins
Teleportation allows Alice to send a pre-prepared quantum state to Bob using only pre-shared entanglement and classical communication. Here we show that it is possible to teleport a state which is also $\it{post}$-selected. Post-selection of a state $\Phi$ means that after Alice has finished her experiment she performs a measurement and only keeps runs of the experiment where the measurement outcome
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Compiling Quantum Circuits for Dynamically Field-Programmable Neutral Atoms Array Processors Quantum (IF 6.4) Pub Date : 2024-03-14 Daniel Bochen Tan, Dolev Bluvstein, Mikhail D. Lukin, Jason Cong
Dynamically field-programmable qubit arrays (DPQA) have recently emerged as a promising platform for quantum information processing. In DPQA, atomic qubits are selectively loaded into arrays of optical traps that can be reconfigured during the computation itself. Leveraging qubit transport and parallel, entangling quantum operations, different pairs of qubits, even those initially far away, can be
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Entanglement Trajectory and its Boundary Quantum (IF 6.4) Pub Date : 2024-03-14 Ruge Lin
In this article, we present a novel approach to investigating entanglement in the context of quantum computing. Our methodology involves analyzing reduced density matrices at different stages of a quantum algorithm's execution and representing the dominant eigenvalue and von Neumann entropy on a graph, creating an "entanglement trajectory." To establish the trajectory's boundaries, we employ random
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A structure theorem for generalized-noncontextual ontological models Quantum (IF 6.4) Pub Date : 2024-03-14 David Schmid, John H. Selby, Matthew F. Pusey, Robert W. Spekkens
It is useful to have a criterion for when the predictions of an operational theory should be considered classically explainable. Here we take the criterion to be that the theory admits of a generalized-noncontextual ontological model. Existing works on generalized noncontextuality have focused on experimental scenarios having a simple structure: typically, prepare-measure scenarios. Here, we formally
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Basic quantum subroutines: finding multiple marked elements and summing numbers Quantum (IF 6.4) Pub Date : 2024-03-14 Joran van Apeldoorn, Sander Gribling, Harold Nieuwboer
We show how to find all $k$ marked elements in a list of size $N$ using the optimal number $O(\sqrt{N k})$ of quantum queries and only a polylogarithmic overhead in the gate complexity, in the setting where one has a small quantum memory. Previous algorithms either incurred a factor $k$ overhead in the gate complexity, or had an extra factor $\log(k)$ in the query complexity. We then consider the problem
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Stabilization of Hubbard-Thouless pumps through nonlocal fermionic repulsion Quantum (IF 6.4) Pub Date : 2024-03-14 Javier Argüello-Luengo, Manfred J. Mark, Francesca Ferlaino, Maciej Lewenstein, Luca Barbiero, Sergi Julià-Farré
Thouless pumping represents a powerful concept to probe quantized topological invariants in quantum systems. We explore this mechanism in a generalized Rice-Mele Fermi-Hubbard model characterized by the presence of competing onsite and intersite interactions. Contrary to recent experimental and theoretical results, showing a breakdown of quantized pumping induced by the onsite repulsion, we prove that
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Quantum circuits for toric code and X-cube fracton model Quantum (IF 6.4) Pub Date : 2024-03-13 Penghua Chen, Bowen Yan, Shawn X. Cui
We propose a systematic and efficient quantum circuit composed solely of Clifford gates for simulating the ground state of the surface code model. This approach yields the ground state of the toric code in $\lceil 2L+2+log_{2}(d)+\frac{L}{2d} \rceil$ time steps, where $L$ refers to the system size and $d$ represents the maximum distance to constrain the application of the CNOT gates. Our algorithm
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Variational Phase Estimation with Variational Fast Forwarding Quantum (IF 6.4) Pub Date : 2024-03-13 Maria-Andreea Filip, David Muñoz Ramo, Nathan Fitzpatrick
Subspace diagonalisation methods have appeared recently as promising means to access the ground state and some excited states of molecular Hamiltonians by classically diagonalising small matrices, whose elements can be efficiently obtained by a quantum computer. The recently proposed Variational Quantum Phase Estimation (VQPE) algorithm uses a basis of real time-evolved states, for which the energy
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Time-optimal multi-qubit gates: Complexity, efficient heuristic and gate-time bounds Quantum (IF 6.4) Pub Date : 2024-03-13 Pascal Baßler, Markus Heinrich, Martin Kliesch
Multi-qubit entangling interactions arise naturally in several quantum computing platforms and promise advantages over traditional two-qubit gates. In particular, a fixed multi-qubit Ising-type interaction together with single-qubit X-gates can be used to synthesize global ZZ-gates (GZZ gates). In this work, we first show that the synthesis of such quantum gates that are time-optimal is NP-hard. Second
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Here comes the SU(N): multivariate quantum gates and gradients Quantum (IF 6.4) Pub Date : 2024-03-07 Roeland Wiersema, Dylan Lewis, David Wierichs, Juan Carrasquilla, Nathan Killoran
Variational quantum algorithms use non-convex optimization methods to find the optimal parameters for a parametrized quantum circuit in order to solve a computational problem. The choice of the circuit ansatz, which consists of parameterized gates, is crucial to the success of these algorithms. Here, we propose a gate which fully parameterizes the special unitary group $\mathrm{SU}(N)$. This gate is
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Ergodicity Breaking Under Confinement in Cold-Atom Quantum Simulators Quantum (IF 6.4) Pub Date : 2024-02-29 Jean-Yves Desaules, Guo-Xian Su, Ian P. McCulloch, Bing Yang, Zlatko Papić, Jad C. Halimeh
The quantum simulation of gauge theories on synthetic quantum matter devices has gained a lot of traction in the last decade, making possible the observation of a range of exotic quantum many-body phenomena. In this work, we consider the spin-$1/2$ quantum link formulation of $1+1$D quantum electrodynamics with a topological $\theta$-angle, which can be used to tune a confinement-deconfinement transition
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Bicolor loop models and their long range entanglement Quantum (IF 6.4) Pub Date : 2024-02-29 Zhao Zhang
Quantum loop models are well studied objects in the context of lattice gauge theories and topological quantum computing. They usually carry long range entanglement that is captured by the topological entanglement entropy. I consider generalization of the toric code model to bicolor loop models and show that the long range entanglement can be reflected in three different ways: a topologically invariant
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Identifying families of multipartite states with non-trivial local entanglement transformations Quantum (IF 6.4) Pub Date : 2024-02-29 Nicky Kai Hong Li, Cornelia Spee, Martin Hebenstreit, Julio I. de Vicente, Barbara Kraus
The study of state transformations by spatially separated parties with local operations assisted by classical communication (LOCC) plays a crucial role in entanglement theory and its applications in quantum information processing. Transformations of this type among pure bipartite states were characterized long ago and have a revealing theoretical structure. However, it turns out that generic fully
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Dynamical quantum phase transitions from random matrix theory Quantum (IF 6.4) Pub Date : 2024-02-29 David Pérez-García, Leonardo Santilli, Miguel Tierz
We uncover a novel dynamical quantum phase transition, using random matrix theory and its associated notion of planar limit. We study it for the isotropic XY Heisenberg spin chain. For this, we probe its real-time dynamics through the Loschmidt echo. This leads to the study of a random matrix ensemble with a complex weight, whose analysis requires novel technical considerations, that we develop. We
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Entanglement-symmetries of covariant channels Quantum (IF 6.4) Pub Date : 2024-02-29 Dominic Verdon
Let $G$ and $G'$ be monoidally equivalent compact quantum groups, and let $H$ be a Hopf-Galois object realising a monoidal equivalence between these groups' representation categories. This monoidal equivalence induces an equivalence Chan($G$) $\rightarrow$ Chan($G'$), where Chan($G$) is the category whose objects are finite-dimensional $C*$-algebras with an action of G and whose morphisms are covariant
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Entanglement dynamics of photon pairs and quantum memories in the gravitational field of the earth Quantum (IF 6.4) Pub Date : 2024-02-29 Roy Barzel, Mustafa Gündoğan, Markus Krutzik, Dennis Rätzel, Claus Lämmerzahl
We investigate the effect of entanglement dynamics due to gravity – the basis of a mechanism of universal decoherence – for photonic states and quantum memories in Mach-Zehnder and Hong-Ou-Mandel interferometry setups in the gravitational field of the earth. We show that chances are good to witness the effect with near-future technology in Hong-Ou-Mandel interferometry. This would represent an experimental
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Towards a measurement theory in QFT: “Impossible” quantum measurements are possible but not ideal Quantum (IF 6.4) Pub Date : 2024-02-27 Nicolas Gisin, Flavio Del Santo
Naive attempts to put together relativity and quantum measurements lead to signaling between space-like separated regions. In QFT, these are known as $\textit{impossible measurements}$. We show that the same problem arises in non-relativistic quantum physics, where joint nonlocal measurements (i.e., between systems kept spatially separated) in general lead to signaling, while one would expect no-signaling
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Improved Accuracy for Trotter Simulations Using Chebyshev Interpolation Quantum (IF 6.4) Pub Date : 2024-02-26 Gumaro Rendon, Jacob Watkins, Nathan Wiebe
Quantum metrology allows for measuring properties of a quantum system at the optimal Heisenberg limit. However, when the relevant quantum states are prepared using digital Hamiltonian simulation, the accrued algorithmic errors will cause deviations from this fundamental limit. In this work, we show how algorithmic errors due to Trotterized time evolution can be mitigated through the use of standard
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Analogue Quantum Simulation with Fixed-Frequency Transmon Qubits Quantum (IF 6.4) Pub Date : 2024-02-22 Sean Greenaway, Adam Smith, Florian Mintert, Daniel Malz
We experimentally assess the suitability of transmon qubits with fixed frequencies and fixed interactions for the realization of analogue quantum simulations of spin systems. We test a set of necessary criteria for this goal on a commercial quantum processor using full quantum process tomography and more efficient Hamiltonian tomography. Significant single qubit errors at low amplitudes are identified
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Accelerating Quantum Algorithms with Precomputation Quantum (IF 6.4) Pub Date : 2024-02-22 William J. Huggins, Jarrod R. McClean
Real-world applications of computing can be extremely time-sensitive. It would be valuable if we could accelerate such tasks by performing some of the work ahead of time. Motivated by this, we propose a cost model for quantum algorithms that allows quantum precomputation; i.e., for a polynomial amount of ``free'' computation before the input to an algorithm is fully specified, and methods for taking
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Quantum Vision Transformers Quantum (IF 6.4) Pub Date : 2024-02-22 El Amine Cherrat, Iordanis Kerenidis, Natansh Mathur, Jonas Landman, Martin Strahm, Yun Yvonna Li
In this work, quantum transformers are designed and analysed in detail by extending the state-of-the-art classical transformer neural network architectures known to be very performant in natural language processing and image analysis. Building upon the previous work, which uses parametrised quantum circuits for data loading and orthogonal neural layers, we introduce three types of quantum transformers
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Stabilizer Formalism for Operator Algebra Quantum Error Correction Quantum (IF 6.4) Pub Date : 2024-02-21 Guillaume Dauphinais, David W. Kribs, Michael Vasmer
We introduce a stabilizer formalism for the general quantum error correction framework called operator algebra quantum error correction (OAQEC), which generalizes Gottesman's formulation for traditional quantum error correcting codes (QEC) and Poulin's for operator quantum error correction and subsystem codes (OQEC). The construction generates hybrid classical-quantum stabilizer codes and we formulate
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Taming the Rotating Wave Approximation Quantum (IF 6.4) Pub Date : 2024-02-21 Daniel Burgarth, Paolo Facchi, Robin Hillier, Marilena Ligabò
The interaction between light and matter is one of the oldest research areas of quantum mechanics, and a field that just keeps on delivering new insights and applications. With the arrival of cavity and circuit quantum electrodynamics we can now achieve strong light-matter couplings which form the basis of most implementations of quantum technology. But quantum information processing also has high
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A hybrid quantum algorithm to detect conical intersections Quantum (IF 6.4) Pub Date : 2024-02-20 Emiel Koridon, Joana Fraxanet, Alexandre Dauphin, Lucas Visscher, Thomas E. O'Brien, Stefano Polla
Conical intersections are topologically protected crossings between the potential energy surfaces of a molecular Hamiltonian, known to play an important role in chemical processes such as photoisomerization and non-radiative relaxation. They are characterized by a non-zero Berry phase, which is a topological invariant defined on a closed path in atomic coordinate space, taking the value $\pi$ when
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Reqomp: Space-constrained Uncomputation for Quantum Circuits Quantum (IF 6.4) Pub Date : 2024-02-19 Anouk Paradis, Benjamin Bichsel, Martin Vechev
Quantum circuits must run on quantum computers with tight limits on qubit and gate counts. To generate circuits respecting both limits, a promising opportunity is exploiting $uncomputation$ to trade qubits for gates. We present Reqomp, a method to automatically synthesize correct and efficient uncomputation of ancillae while respecting hardware constraints. For a given circuit, Reqomp can offer a wide
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Photonic entanglement during a zero-g flight Quantum (IF 6.4) Pub Date : 2024-02-15 Julius Arthur Bittermann, Lukas Bulla, Sebastian Ecker, Sebastian Philipp Neumann, Matthias Fink, Martin Bohmann, Nicolai Friis, Marcus Huber, Rupert Ursin
Quantum technologies have matured to the point that we can test fundamental quantum phenomena under extreme conditions. Specifically, entanglement, a cornerstone of modern quantum information theory, can be robustly produced and verified in various adverse environments. We take these tests further and implement a high-quality Bell experiment during a parabolic flight, transitioning from microgravity
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Quantitative relations between different measurement contexts Quantum (IF 6.4) Pub Date : 2024-02-14 Ming Ji, Holger F. Hofmann
In quantum theory, a measurement context is defined by an orthogonal basis in a Hilbert space, where each basis vector represents a specific measurement outcome. The precise quantitative relation between two different measurement contexts can thus be characterized by the inner products of nonorthogonal states in that Hilbert space. Here, we use measurement outcomes that are shared by different contexts
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Continuous-time quantum walks for MAX-CUT are hot Quantum (IF 6.4) Pub Date : 2024-02-13 Robert J. Banks, Ehsan Haque, Farah Nazef, Fatima Fethallah, Fatima Ruqaya, Hamza Ahsan, Het Vora, Hibah Tahir, Ibrahim Ahmad, Isaac Hewins, Ishaq Shah, Krish Baranwal, Mannan Arora, Mateen Asad, Mubasshirah Khan, Nabian Hasan, Nuh Azad, Salgai Fedaiee, Shakeel Majeed, Shayam Bhuyan, Tasfia Tarannum, Yahya Ali, Dan E. Browne, P. A. Warburton
By exploiting the link between time-independent Hamiltonians and thermalisation, heuristic predictions on the performance of continuous-time quantum walks for MAX-CUT are made. The resulting predictions depend on the number of triangles in the underlying MAX-CUT graph. We extend these results to the time-dependent setting with multi-stage quantum walks and Floquet systems. The approach followed here
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Incompatibility of quantum instruments Quantum (IF 6.4) Pub Date : 2024-02-12 Leevi Leppäjärvi, Michal Sedlák
Quantum instruments describe outcome probability as well as state change induced by measurement of a quantum system. Incompatibility of two instruments, i. e. the impossibility to realize them simultaneously on a given quantum system, generalizes incompatibility of channels and incompatibility of positive operator-valued measures (POVMs). We derive implications of instrument compatibility for the induced
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Gravitational quantum switch on a superposition of spherical shells Quantum (IF 6.4) Pub Date : 2024-02-12 Natália S. Móller, Bruna Sahdo, Nelson Yokomizo
In the absence of a complete theory of quantum gravity, phenomenological models built upon minimal assumptions have been explored for the analysis of possible quantum effects in gravitational systems. Implications of a superposition of geometries have been considered in such models, including the occurrence of processes with indefinite order. In a gravitational quantum switch, in particular, the order
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Stabilizer Codes with Exotic Local-dimensions Quantum (IF 6.4) Pub Date : 2024-02-12 Lane G. Gunderman
Traditional stabilizer codes operate over prime power local-dimensions. In this work we extend the stabilizer formalism using the local-dimension-invariant setting to import stabilizer codes from these standard local-dimensions to other cases. In particular, we show that any traditional stabilizer code can be used for analog continuous-variable codes, and consider restrictions in phase space and discretized
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Efficient learning of $t$-doped stabilizer states with single-copy measurements Quantum (IF 6.4) Pub Date : 2024-02-12 Nai-Hui Chia, Ching-Yi Lai, Han-Hsuan Lin
One of the primary objectives in the field of quantum state learning is to develop algorithms that are time-efficient for learning states generated from quantum circuits. Earlier investigations have demonstrated time-efficient algorithms for states generated from Clifford circuits with at most $\log(n)$ non-Clifford gates. However, these algorithms necessitate multi-copy measurements, posing implementation
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Impact of conditional modelling for a universal autoregressive quantum state Quantum (IF 6.4) Pub Date : 2024-02-08 Massimo Bortone, Yannic Rath, George H. Booth
We present a generalized framework to adapt universal quantum state approximators, enabling them to satisfy rigorous normalization and autoregressive properties. We also introduce filters as analogues to convolutional layers in neural networks to incorporate translationally symmetrized correlations in arbitrary quantum states. By applying this framework to the Gaussian process state, we enforce autoregressive
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Efficient classical simulation of cluster state quantum circuits with alternative inputs Quantum (IF 6.4) Pub Date : 2024-02-06 Sahar Atallah, Michael Garn, Sania Jevtic, Yukuan Tao, Shashank Virmani
We provide new examples of pure entangled systems related to cluster state quantum computation that can be efficiently simulated classically. In cluster state quantum computation input qubits are initialised in the `equator' of the Bloch sphere, $CZ$ gates are applied, and finally the qubits are measured adaptively using $Z$ measurements or measurements of $\cos(\theta)X + \sin(\theta)Y$ operators
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Coherence and contextuality in a Mach-Zehnder interferometer Quantum (IF 6.4) Pub Date : 2024-02-05 Rafael Wagner, Anita Camillini, Ernesto F. Galvão
We analyse nonclassical resources in interference phenomena using generalized noncontextuality inequalities and basis-independent coherence witnesses. We use recently proposed inequalities that witness both resources within the same framework. We also propose, in view of previous contextual advantage results, a systematic way of applying these tools to characterize advantage provided by coherence and
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No-signalling constrains quantum computation with indefinite causal structure Quantum (IF 6.4) Pub Date : 2024-02-05 Luca Apadula, Alessandro Bisio, Paolo Perinotti
Quantum processes with indefinite causal structure emerge when we wonder which are the most general evolutions, allowed by quantum theory, of a set of local systems which are not assumed to be in any particular causal order. These processes can be described within the framework of $higher-order$ quantum theory which, starting from considering maps from quantum transformations to quantum transformations
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Hamiltonian variational ansatz without barren plateaus Quantum (IF 6.4) Pub Date : 2024-02-01 Chae-Yeun Park, Nathan Killoran
Variational quantum algorithms, which combine highly expressive parameterized quantum circuits (PQCs) and optimization techniques in machine learning, are one of the most promising applications of a near-term quantum computer. Despite their huge potential, the utility of variational quantum algorithms beyond tens of qubits is still questioned. One of the central problems is the trainability of PQCs
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Persistent Tensors and Multiqudit Entanglement Transformation Quantum (IF 6.4) Pub Date : 2024-01-31 Masoud Gharahi, Vladimir Lysikov
We construct a lower bound of the tensor rank for a new class of tensors, which we call $\textit{persistent tensors}$. We present three specific families of persistent tensors, of which the lower bound is tight. We show that there is a chain of degenerations between these three families of minimal-rank persistent tensors that can be used to study the entanglement transformation between them. In addition
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Bounding entanglement dimensionality from the covariance matrix Quantum (IF 6.4) Pub Date : 2024-01-30 Shuheng Liu, Matteo Fadel, Qiongyi He, Marcus Huber, Giuseppe Vitagliano
High-dimensional entanglement has been identified as an important resource in quantum information processing, and also as a main obstacle for simulating quantum systems. Its certification is often difficult, and most widely used methods for experiments are based on fidelity measurements with respect to highly entangled states. Here, instead, we consider covariances of collective observables, as in
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Chain-mapping methods for relativistic light-matter interactions Quantum (IF 6.4) Pub Date : 2024-01-30 Robert H. Jonsson, Johannes Knörzer
The interaction between localized emitters and quantum fields, both in relativistic settings and in the case of ultra-strong couplings, requires non-perturbative methods beyond the rotating-wave approximation. In this work we employ chain-mapping methods to achieve a numerically exact treatment of the interaction between a localized emitter and a scalar quantum field. We extend the application range
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Orthonormal bases of extreme quantumness Quantum (IF 6.4) Pub Date : 2024-01-25 Marcin Rudziński, Adam Burchardt, Karol Życzkowski
Spin anticoherent states acquired recently a lot of attention as the most "quantum" states. Some coherent and anticoherent spin states are known as optimal quantum rotosensors. In this work, we introduce a measure of quantumness for orthonormal bases of spin states, determined by the average anticoherence of individual vectors and the Wehrl entropy. In this way, we identify the most coherent and most
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A complete and operational resource theory of measurement sharpness Quantum (IF 6.4) Pub Date : 2024-01-25 Francesco Buscemi, Kodai Kobayashi, Shintaro Minagawa
We construct a resource theory of $sharpness$ for finite-dimensional positive operator-valued measures (POVMs), where the $sharpness-non-increasing$ operations are given by quantum preprocessing channels and convex mixtures with POVMs whose elements are all proportional to the identity operator. As required for a sound resource theory of sharpness, we show that our theory has maximal (i.e., sharp)
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A new quantum machine learning algorithm: split hidden quantum Markov model inspired by quantum conditional master equation Quantum (IF 6.4) Pub Date : 2024-01-24 Xiao-Yu Li, Qin-Sheng Zhu, Yong Hu, Hao Wu, Guo-Wu Yang, Lian-Hui Yu, Geng Chen
The Hidden Quantum Markov Model (HQMM) has significant potential for analyzing time-series data and studying stochastic processes in the quantum domain as an upgrading option with potential advantages over classical Markov models. In this paper, we introduced the split HQMM (SHQMM) for implementing the hidden quantum Markov process, utilizing the conditional master equation with a fine balance condition
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Entanglement Purification with Quantum LDPC Codes and Iterative Decoding Quantum (IF 6.4) Pub Date : 2024-01-24 Narayanan Rengaswamy, Nithin Raveendran, Ankur Raina, Bane Vasić
Recent constructions of quantum low-density parity-check (QLDPC) codes provide optimal scaling of the number of logical qubits and the minimum distance in terms of the code length, thereby opening the door to fault-tolerant quantum systems with minimal resource overhead. However, the hardware path from nearest-neighbor-connection-based topological codes to long-range-interaction-demanding QLDPC codes
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Parameter Setting in Quantum Approximate Optimization of Weighted Problems Quantum (IF 6.4) Pub Date : 2024-01-18 Shree Hari Sureshbabu, Dylan Herman, Ruslan Shaydulin, Joao Basso, Shouvanik Chakrabarti, Yue Sun, Marco Pistoia
Quantum Approximate Optimization Algorithm (QAOA) is a leading candidate algorithm for solving combinatorial optimization problems on quantum computers. However, in many cases QAOA requires computationally intensive parameter optimization. The challenge of parameter optimization is particularly acute in the case of weighted problems, for which the eigenvalues of the phase operator are non-integer and
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Parallel Quantum Algorithm for Hamiltonian Simulation Quantum (IF 6.4) Pub Date : 2024-01-15 Zhicheng Zhang, Qisheng Wang, Mingsheng Ying
We study how parallelism can speed up quantum simulation. A parallel quantum algorithm is proposed for simulating the dynamics of a large class of Hamiltonians with good sparse structures, called uniform-structured Hamiltonians, including various Hamiltonians of practical interest like local Hamiltonians and Pauli sums. Given the oracle access to the target sparse Hamiltonian, in both query and gate
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The complexity of quantum support vector machines Quantum (IF 6.4) Pub Date : 2024-01-11 Gian Gentinetta, Arne Thomsen, David Sutter, Stefan Woerner
Quantum support vector machines employ quantum circuits to define the kernel function. It has been shown that this approach offers a provable exponential speedup compared to any known classical algorithm for certain data sets. The training of such models corresponds to solving a convex optimization problem either via its primal or dual formulation. Due to the probabilistic nature of quantum mechanics
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Block-encoding structured matrices for data input in quantum computing Quantum (IF 6.4) Pub Date : 2024-01-11 Christoph Sünderhauf, Earl Campbell, Joan Camps
The cost of data input can dominate the run-time of quantum algorithms. Here, we consider data input of arithmetically structured matrices via $\textit{block encoding}$ circuits, the input model for the quantum singular value transform and related algorithms. We demonstrate how to construct block encoding circuits based on an arithmetic description of the sparsity and pattern of repeated values of
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Microcanonical windows on quantum operators Quantum (IF 6.4) Pub Date : 2024-01-11 Silvia Pappalardi, Laura Foini, Jorge Kurchan
We discuss the construction of a microcanonical projection WOW of a quantum operator O induced by an energy window filter W, its spectrum, and the retrieval of canonical many-time correlations from it.
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Efficient Verification of Ground States of Frustration-Free Hamiltonians Quantum (IF 6.4) Pub Date : 2024-01-10 Huangjun Zhu, Yunting Li, Tianyi Chen
Ground states of local Hamiltonians are of key interest in many-body physics and also in quantum information processing. Efficient verification of these states are crucial to many applications, but very challenging. Here we propose a simple, but powerful recipe for verifying the ground states of general frustration-free Hamiltonians based on local measurements. Moreover, we derive rigorous bounds on
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Resource engines Quantum (IF 6.4) Pub Date : 2024-01-10 Hanna Wojewódka-Ściążko, Zbigniew Puchała, Kamil Korzekwa
In this paper we aim to push the analogy between thermodynamics and quantum resource theories one step further. Previous inspirations were based predominantly on thermodynamic considerations concerning scenarios with a single heat bath, neglecting an important part of thermodynamics that studies heat engines operating between two baths at different temperatures. Here, we investigate the performance
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Energy densities in quantum mechanics Quantum (IF 6.4) Pub Date : 2024-01-10 V. Stepanyan, A.E. Allahverdyan
Quantum mechanics does not provide any ready recipe for defining energy density in space, since the energy and coordinate do not commute. To find a well-motivated energy density, we start from a possibly fundamental, relativistic description for a spin-$\frac{1}{2}$ particle: Dirac's equation. Employing its energy-momentum tensor and going to the non-relativistic limit we find a locally conserved non-relativistic
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Witnessing environment dimension through temporal correlations Quantum (IF 6.4) Pub Date : 2024-01-10 Lucas B. Vieira, Simon Milz, Giuseppe Vitagliano, Costantino Budroni
We introduce a framework to compute upper bounds for temporal correlations achievable in open quantum system dynamics, obtained by repeated measurements on the system. As these correlations arise by virtue of the environment acting as a memory resource, such bounds are witnesses for the minimal dimension of an effective environment compatible with the observed statistics. These witnesses are derived
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A review and reformulation of macroscopic realism: resolving its deficiencies using the framework of generalized probabilistic theories Quantum (IF 6.4) Pub Date : 2024-01-03 David Schmid
The notion of macrorealism was introduced by Leggett and Garg in an attempt to capture our intuitive conception of the macroscopic world, which seems difficult to reconcile with our knowledge of quantum physics. By now, numerous experimental witnesses have been proposed as methods of falsifying macrorealism. In this work, I critically review and analyze both the definition of macrorealism and the various
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Quantum-optimal information encoding using noisy passive linear optics Quantum (IF 6.4) Pub Date : 2024-01-04 Andrew Tanggara, Ranjith Nair, Syed Assad, Varun Narasimhachar, Spyros Tserkis, Jayne Thompson, Ping Koy Lam, Mile Gu
The amount of information that a noisy channel can transmit has been one of the primary subjects of interest in information theory. In this work we consider a practically-motivated family of optical quantum channels that can be implemented without an external energy source. We optimize the Holevo information over procedures that encode information in attenuations and phase-shifts applied by these channels
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A full circuit-based quantum algorithm for excited-states in quantum chemistry Quantum (IF 6.4) Pub Date : 2024-01-04 Jingwei Wen, Zhengan Wang, Chitong Chen, Junxiang Xiao, Hang Li, Ling Qian, Zhiguo Huang, Heng Fan, Shijie Wei, Guilu Long
Utilizing quantum computer to investigate quantum chemistry is an important research field nowadays. In addition to the ground-state problems that have been widely studied, the determination of excited-states plays a crucial role in the prediction and modeling of chemical reactions and other physical processes. Here, we propose a non-variational full circuit-based quantum algorithm for obtaining the
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Earthquake Quantization Quantum (IF 6.4) Pub Date : 2024-01-02 Benjamin Koch, Enrique Muñoz
In this homage to Einstein's 144th birthday we propose a novel quantization prescription, where the paths of a path-integral are not random, but rather solutions of a geodesic equation in a random background. We show that this change of perspective can be made mathematically equivalent to the usual formulations of non-relativistic quantum mechanics. To conclude, we comment on conceptual issues, such
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Determining the ability for universal quantum computing: Testing controllability via dimensional expressivity Quantum (IF 6.4) Pub Date : 2023-12-21 Fernando Gago-Encinas, Tobias Hartung, Daniel M. Reich, Karl Jansen, Christiane P. Koch
Operator controllability refers to the ability to implement an arbitrary unitary in SU(N) and is a prerequisite for universal quantum computing. Controllability tests can be used in the design of quantum devices to reduce the number of external controls. Their practical use is hampered, however, by the exponential scaling of their numerical effort with the number of qubits. Here, we devise a hybrid