-
Warm-Started QAOA with Custom Mixers Provably Converges and Computationally Beats Goemans-Williamson’s Max-Cut at Low Circuit Depths Quantum (IF 6.4) Pub Date : 2023-09-26 Reuben Tate, Jai Moondra, Bryan Gard, Greg Mohler, Swati Gupta
We generalize the Quantum Approximate Optimization Algorithm (QAOA) of Farhi et al. (2014) to allow for arbitrary separable initial states with corresponding mixers such that the starting state is the most excited state of the mixing Hamiltonian. We demonstrate this version of QAOA, which we call $QAOA-warmest$, by simulating Max-Cut on weighted graphs. We initialize the starting state as a $warm-start$
-
Correcting non-independent and non-identically distributed errors with surface codes Quantum (IF 6.4) Pub Date : 2023-09-26 Konstantin Tiurev, Peter-Jan H. S. Derks, Joschka Roffe, Jens Eisert, Jan-Michael Reiner
A common approach to studying the performance of quantum error correcting codes is to assume independent and identically distributed single-qubit errors. However, the available experimental data shows that realistic errors in modern multi-qubit devices are typically neither independent nor identical across qubits. In this work, we develop and investigate the properties of topological surface codes
-
Pure non-Markovian evolutions Quantum (IF 6.4) Pub Date : 2023-09-26 Dario De Santis
Non-Markovian dynamics are characterized by information backflows, where the evolving open quantum system retrieves part of the information previously lost in the environment. Hence, the very definition of non-Markovianity implies an initial time interval when the evolution is noisy, otherwise no backflow could take place. We identify two types of initial noise, where the first has the only effect
-
Analysis of arbitrary superconducting quantum circuits accompanied by a Python package: SQcircuit Quantum (IF 6.4) Pub Date : 2023-09-25 Taha Rajabzadeh, Zhaoyou Wang, Nathan Lee, Takuma Makihara, Yudan Guo, Amir H. Safavi-Naeini
Superconducting quantum circuits are a promising hardware platform for realizing a fault-tolerant quantum computer. Accelerating progress in this field of research demands general approaches and computational tools to analyze and design more complex superconducting circuits. We develop a framework to systematically construct a superconducting quantum circuit's quantized Hamiltonian from its physical
-
Why interference phenomena do not capture the essence of quantum theory Quantum (IF 6.4) Pub Date : 2023-09-25 Lorenzo Catani, Matthew Leifer, David Schmid, Robert W. Spekkens
Quantum interference phenomena are widely viewed as posing a challenge to the classical worldview. Feynman even went so far as to proclaim that they are the $\textit{only mystery}$ and the $\textit{basic peculiarity}$ of quantum mechanics. Many have also argued that basic interference phenomena force us to accept a number of radical interpretational conclusions, including: that a photon is neither
-
Testing symmetry on quantum computers Quantum (IF 6.4) Pub Date : 2023-09-25 Margarite L. LaBorde, Soorya Rethinasamy, Mark M. Wilde
Symmetry is a unifying concept in physics. In quantum information and beyond, it is known that quantum states possessing symmetry are not useful for certain information-processing tasks. For example, states that commute with a Hamiltonian realizing a time evolution are not useful for timekeeping during that evolution, and bipartite states that are highly extendible are not strongly entangled and thus
-
Anonymous conference key agreement in linear quantum networks Quantum (IF 6.4) Pub Date : 2023-09-21 Jarn de Jong, Frederik Hahn, Jens Eisert, Nathan Walk, Anna Pappa
Sharing multi-partite quantum entanglement between parties allows for diverse secure communication tasks to be performed. Among them, conference key agreement (CKA) - an extension of key distribution to multiple parties - has received much attention recently. Interestingly, CKA can also be performed in a way that protects the identities of the participating parties, therefore providing $anonymity$
-
Quantum Gauge Networks: A New Kind of Tensor Network Quantum (IF 6.4) Pub Date : 2023-09-14 Kevin Slagle
Although tensor networks are powerful tools for simulating low-dimensional quantum physics, tensor network algorithms are very computationally costly in higher spatial dimensions. We introduce $\textit{quantum gauge networks}$: a different kind of tensor network ansatz for which the computation cost of simulations does not explicitly increase for larger spatial dimensions. We take inspiration from
-
Random unitaries, Robustness, and Complexity of Entanglement Quantum (IF 6.4) Pub Date : 2023-09-15 J. Odavić, G. Torre, N. Mijić, D. Davidović, F. Franchini, S. M. Giampaolo
It is widely accepted that the dynamic of entanglement in presence of a generic circuit can be predicted by the knowledge of the statistical properties of the entanglement spectrum. We tested this assumption by applying a Metropolis-like entanglement cooling algorithm generated by different sets of local gates, on states sharing the same statistic. We employ the ground states of a unique model, namely
-
Testing identity of collections of quantum states: sample complexity analysis Quantum (IF 6.4) Pub Date : 2023-09-11 Marco Fanizza, Raffaele Salvia, Vittorio Giovannetti
We study the problem of testing identity of a collection of unknown quantum states given sample access to this collection, each state appearing with some known probability. We show that for a collection of $d$-dimensional quantum states of cardinality $N$, the sample complexity is $O(\sqrt{N}d/\epsilon^2)$, with a matching lower bound, up to a multiplicative constant. The test is obtained by estimating
-
Forging quantum data: classically defeating an IQP-based quantum test Quantum (IF 6.4) Pub Date : 2023-09-11 Gregory D. Kahanamoku-Meyer
Recently, quantum computing experiments have for the first time exceeded the capability of classical computers to perform certain computations – a milestone termed "quantum computational advantage." However, verifying the output of the quantum device in these experiments required extremely large classical computations. An exciting next step for demonstrating quantum capability would be to implement
-
LIMDD: A Decision Diagram for Simulation of Quantum Computing Including Stabilizer States Quantum (IF 6.4) Pub Date : 2023-09-11 Lieuwe Vinkhuijzen, Tim Coopmans, David Elkouss, Vedran Dunjko, Alfons Laarman
Efficient methods for the representation and simulation of quantum states and quantum operations are crucial for the optimization of quantum circuits. Decision diagrams (DDs), a well-studied data structure originally used to represent Boolean functions, have proven capable of capturing relevant aspects of quantum systems, but their limits are not well understood. In this work, we investigate and bridge
-
Noise-robust ground state energy estimates from deep quantum circuits Quantum (IF 6.4) Pub Date : 2023-09-11 Harish J. Vallury, Michael A. Jones, Gregory A. L. White, Floyd M. Creevey, Charles D. Hill, Lloyd C. L. Hollenberg
In the lead up to fault tolerance, the utility of quantum computing will be determined by how adequately the effects of noise can be circumvented in quantum algorithms. Hybrid quantum-classical algorithms such as the variational quantum eigensolver (VQE) have been designed for the short-term regime. However, as problems scale, VQE results are generally scrambled by noise on present-day hardware. While
-
A Multi-Qubit Quantum Gate Using the Zeno Effect Quantum (IF 6.4) Pub Date : 2023-09-07 Philippe Lewalle, Leigh S. Martin, Emmanuel Flurin, Song Zhang, Eliya Blumenthal, Shay Hacohen-Gourgy, Daniel Burgarth, K. Birgitta Whaley
The Zeno effect, in which repeated observation freezes the dynamics of a quantum system, stands as an iconic oddity of quantum mechanics. When a measurement is unable to distinguish between states in a subspace, the dynamics within that subspace can be profoundly altered, leading to non-trivial behavior. Here we show that such a measurement can turn a non-interacting system with only single-qubit control
-
Bounds on the smallest sets of quantum states with special quantum nonlocality Quantum (IF 6.4) Pub Date : 2023-09-07 Mao-Sheng Li, Yan-Ling Wang
An orthogonal set of states in multipartite systems is called to be strong quantum nonlocality if it is locally irreducible under every bipartition of the subsystems [46]. In this work, we study a subclass of locally irreducible sets: the only possible orthogonality preserving measurement on each subsystems are trivial measurements. We call the set with this property is locally stable. We find that
-
On a gap in the proof of the generalised quantum Stein’s lemma and its consequences for the reversibility of quantum resources Quantum (IF 6.4) Pub Date : 2023-09-07 Mario Berta, Fernando G. S. L. Brandão, Gilad Gour, Ludovico Lami, Martin B. Plenio, Bartosz Regula, Marco Tomamichel
We show that the proof of the generalised quantum Stein's lemma [Brandão & Plenio, Commun. Math. Phys. 295, 791 (2010)] is not correct due to a gap in the argument leading to Lemma III.9. Hence, the main achievability result of Brandão & Plenio is not known to hold. This puts into question a number of established results in the literature, in particular the reversibility of quantum entanglement [Brandão
-
Energy-efficient quantum non-demolition measurement with a spin-photon interface Quantum (IF 6.4) Pub Date : 2023-08-31 Maria Maffei, Bruno O. Goes, Stephen C. Wein, Andrew N. Jordan, Loïc Lanco, Alexia Auffèves
Spin-photon interfaces (SPIs) are key devices of quantum technologies, aimed at coherently transferring quantum information between spin qubits and propagating pulses of polarized light. We study the potential of a SPI for quantum non demolition (QND) measurements of a spin state. After being initialized and scattered by the SPI, the state of a light pulse depends on the spin state. It thus plays the
-
A Quadratic Speedup in the Optimization of Noisy Quantum Optical Circuits Quantum (IF 6.4) Pub Date : 2023-08-29 Robbe De Prins, Yuan Yao, Anuj Apte, Filippo M. Miatto
Linear optical quantum circuits with photon number resolving (PNR) detectors are used for both Gaussian Boson Sampling (GBS) and for the preparation of non-Gaussian states such as Gottesman-Kitaev-Preskill (GKP), cat and NOON states. They are crucial in many schemes of quantum computing and quantum metrology. Classically optimizing circuits with PNR detectors is challenging due to their exponentially
-
Quantum reference frames: derivation of perspective-dependent descriptions via a perspective-neutral structure Quantum (IF 6.4) Pub Date : 2023-08-29 Viktor Zelezny
In standard quantum mechanics, reference frames are treated as abstract entities. We can think of them as idealized, infinite-mass subsystems which decouple from the rest of the system. In nature, however, all reference frames are realized through finite-mass systems that are subject to the laws of quantum mechanics and must be included in the dynamical evolution. A fundamental physical theory should
-
Local Probabilistic Decoding of a Quantum Code Quantum (IF 6.4) Pub Date : 2023-08-29 T. R. Scruby, K. Nemoto
$\tt{flip}$ is an extremely simple and maximally local classical decoder which has been used to great effect in certain classes of classical codes. When applied to quantum codes there exist constant-weight errors (such as half of a stabiliser) which are uncorrectable for this decoder, so previous studies have considered modified versions of $\tt{flip}$, sometimes in conjunction with other decoders
-
Tight Cramér-Rao type bounds for multiparameter quantum metrology through conic programming Quantum (IF 6.4) Pub Date : 2023-08-29 Masahito Hayashi, Yingkai Ouyang
In the quest to unlock the maximum potential of quantum sensors, it is of paramount importance to have practical measurement strategies that can estimate incompatible parameters with best precisions possible. However, it is still not known how to find practical measurements with optimal precisions, even for uncorrelated measurements over probe states. Here, we give a concrete way to find uncorrelated
-
Refined finite-size analysis of binary-modulation continuous-variable quantum key distribution Quantum (IF 6.4) Pub Date : 2023-08-29 Takaya Matsuura, Shinichiro Yamano, Yui Kuramochi, Toshihiko Sasaki, Masato Koashi
Recent studies showed the finite-size security of binary-modulation CV-QKD protocols against general attacks. However, they gave poor key-rate scaling against transmission distance. Here, we extend the security proof based on complementarity, which is used in the discrete-variable QKD, to the previously developed binary-modulation CV-QKD protocols with the reverse reconciliation under the finite-size
-
Learning ground states of gapped quantum Hamiltonians with Kernel Methods Quantum (IF 6.4) Pub Date : 2023-08-29 Clemens Giuliani, Filippo Vicentini, Riccardo Rossi, Giuseppe Carleo
Neural network approaches to approximate the ground state of quantum hamiltonians require the numerical solution of a highly nonlinear optimization problem. We introduce a statistical learning approach that makes the optimization trivial by using kernel methods. Our scheme is an approximate realization of the power method, where supervised learning is used to learn the next step of the power iteration
-
Stabilizer entropies and nonstabilizerness monotones Quantum (IF 6.4) Pub Date : 2023-08-28 Tobias Haug, Lorenzo Piroli
We study different aspects of the stabilizer entropies (SEs) and compare them against known nonstabilizerness monotones such as the min-relative entropy and the robustness of magic. First, by means of explicit examples, we show that, for Rényi index $0\leq n\leq2$, the SEs are not monotones with respect to stabilizer protocols which include computational-basis measurements, not even when restricting
-
Switching quantum reference frames in the N-body problem and the absence of global relational perspectives Quantum (IF 6.4) Pub Date : 2023-08-22 Augustin Vanrietvelde, Philipp A. Höhn, Flaminia Giacomini
Given the importance of quantum reference frames (QRFs) to both quantum and gravitational physics, it is pertinent to develop a systematic method for switching between the descriptions of physics relative to different choices of QRFs, which is valid in both fields. Here we continue with such a unifying approach, begun in [Quantum 4, 225 (2020)], whose key ingredient is a symmetry principle, which enforces
-
Concatenation Schemes for Topological Fault-tolerant Quantum Error Correction Quantum (IF 6.4) Pub Date : 2023-08-22 Zhaoyi Li, Isaac Kim, Patrick Hayden
We investigate a family of fault-tolerant quantum error correction schemes based on the concatenation of small error detection or error correction codes with the three-dimensional cluster state. We propose fault-tolerant state preparation and decoding schemes that effectively convert every circuit-level error into an erasure error, leveraging the cluster state's high threshold against such errors.
-
A coherence-witnessing game and applications to semi-device-independent quantum key distribution Quantum (IF 6.4) Pub Date : 2023-08-22 Mário Silva, Ricardo Faleiro, Paulo Mateus, Emmanuel Zambrini Cruzeiro
Semi-device-independent quantum key distribution aims to achieve a balance between the highest level of security, device independence, and experimental feasibility. Semi-quantum key distribution presents an intriguing approach that seeks to minimize users' reliance on quantum operations while maintaining security, thus enabling the development of simplified and hardware fault-tolerant quantum protocols
-
Modified dipole-dipole interactions in the presence of a nanophotonic waveguide Quantum (IF 6.4) Pub Date : 2023-08-22 Mathias B. M. Svendsen, Beatriz Olmos
When an emitter ensemble interacts with the electromagnetic field, dipole-dipole interactions are induced between the emitters. The magnitude and shape of these interactions are fully determined by the specific form of the electromagnetic field modes. If the emitters are placed in the vicinity of a nanophotonic waveguide, such as a cylindrical nanofiber, the complex functional form of these modes makes
-
How to perform the coherent measurement of a curved phase space by continuous isotropic measurement. I. Spin and the Kraus-operator geometry of $\mathrm{SL}(2,\mathbb{C})$ Quantum (IF 6.4) Pub Date : 2023-08-16 Christopher S. Jackson, Carlton M. Caves
The generalized $Q$-function of a spin system can be considered the outcome probability distribution of a state subjected to a measurement represented by the spin-coherent-state (SCS) positive-operator-valued measure (POVM). As fundamental as the SCS POVM is to the 2-sphere phase-space representation of spin systems, it has only recently been reported that the SCS POVM can be performed for any spin
-
Assessment of various Hamiltonian partitionings for the electronic structure problem on a quantum computer using the Trotter approximation Quantum (IF 6.4) Pub Date : 2023-08-16 Luis A. Martínez-Martínez, Tzu-Ching Yen, Artur F. Izmaylov
Solving the electronic structure problem via unitary evolution of the electronic Hamiltonian is one of the promising applications of digital quantum computers. One of the practical strategies to implement the unitary evolution is via Trotterization, where a sequence of short-time evolutions of fast-forwardable (i.e. efficiently diagonalizable) Hamiltonian fragments is used. Given multiple choices of
-
A Converse for Fault-tolerant Quantum Computation Quantum (IF 6.4) Pub Date : 2023-08-16 Uthirakalyani G, Anuj K. Nayak, Avhishek Chatterjee
As techniques for fault-tolerant quantum computation keep improving, it is natural to ask: what is the fundamental lower bound on space overhead? In this paper, we obtain a lower bound on the space overhead required for $\epsilon$-accurate implementation of a large class of operations that includes unitary operators. For the practically relevant case of sub-exponential depth and sub-linear gate size
-
Optimal encoding of oscillators into more oscillators Quantum (IF 6.4) Pub Date : 2023-08-16 Jing Wu, Anthony J. Brady, Quntao Zhuang
Bosonic encoding of quantum information into harmonic oscillators is a hardware efficient approach to battle noise. In this regard, oscillator-to-oscillator codes not only provide an additional opportunity in bosonic encoding, but also extend the applicability of error correction to continuous-variable states ubiquitous in quantum sensing and communication. In this work, we derive the optimal osci
-
Thermal Area Law for Lattice Bosons Quantum (IF 6.4) Pub Date : 2023-08-16 Marius Lemm, Oliver Siebert
A physical system is said to satisfy a thermal area law if the mutual information between two adjacent regions in the Gibbs state is controlled by the area of their boundary. Lattice bosons have recently gained significant interest because they can be precisely tuned in experiments and bosonic codes can be employed in quantum error correction to circumvent classical no-go theorems. However, the proofs
-
Nearly-frustration-free ground state preparation Quantum (IF 6.4) Pub Date : 2023-08-16 Matthew Thibodeau, Bryan K. Clark
Solving for quantum ground states is important for understanding the properties of quantum many-body systems, and quantum computers are potentially well-suited for solving for quantum ground states. Recent work [1] has presented a nearly optimal scheme that prepares ground states on a quantum computer for completely generic Hamiltonians, whose query complexity scales as $\delta^{-1}$, i.e. inversely
-
High Dimensional Quantum Machine Learning With Small Quantum Computers Quantum (IF 6.4) Pub Date : 2023-08-09 Simon C. Marshall, Casper Gyurik, Vedran Dunjko
Quantum computers hold great promise to enhance machine learning, but their current qubit counts restrict the realisation of this promise. To deal with this limitation the community has produced a set of techniques for evaluating large quantum circuits on smaller quantum devices. These techniques work by evaluating many smaller circuits on the smaller machine, that are then combined in a polynomial
-
Code-routing: a new attack on position verification Quantum (IF 6.4) Pub Date : 2023-08-09 Joy Cree, Alex May
The cryptographic task of position verification attempts to verify one party's location in spacetime by exploiting constraints on quantum information and relativistic causality. A popular verification scheme known as $f$-routing involves requiring the prover to redirect a quantum system based on the value of a Boolean function $f$. Cheating strategies for the $f$-routing scheme require the prover use
-
Correlations constrained by composite measurements Quantum (IF 6.4) Pub Date : 2023-08-10 John H. Selby, Ana Belén Sainz, Victor Magron, Łukasz Czekaj, Michał Horodecki
How to understand the set of correlations admissible in nature is one outstanding open problem in the core of the foundations of quantum theory. Here we take a complementary viewpoint to the device-independent approach, and explore the correlations that physical theories may feature when restricted by some particular constraints on their measurements. We show that demanding that a theory exhibits a
-
Optimizing sparse fermionic Hamiltonians Quantum (IF 6.4) Pub Date : 2023-08-10 Yaroslav Herasymenko, Maarten Stroeks, Jonas Helsen, Barbara Terhal
We consider the problem of approximating the ground state energy of a fermionic Hamiltonian using a Gaussian state. In sharp contrast to the dense case [1, 2], we prove that strictly $q$-local $\rm {\textit {sparse}}$ fermionic Hamiltonians have a constant Gaussian approximation ratio; the result holds for any connectivity and interaction strengths. Sparsity means that each fermion participates in
-
Adaptive syndrome measurements for Shor-style error correction Quantum (IF 6.4) Pub Date : 2023-08-08 Theerapat Tansuwannont, Balint Pato, Kenneth R. Brown
The Shor fault-tolerant error correction (FTEC) scheme uses transversal gates and ancilla qubits prepared in the cat state in syndrome extraction circuits to prevent propagation of errors caused by gate faults. For a stabilizer code of distance $d$ that can correct up to $t=\lfloor(d-1)/2\rfloor$ errors, the traditional Shor scheme handles ancilla preparation and measurement faults by performing syndrome
-
Classical models may be a better explanation of the Jiuzhang 1.0 Gaussian Boson Sampler than its targeted squeezed light model Quantum (IF 6.4) Pub Date : 2023-08-08 Javier Martínez-Cifuentes, K. M. Fonseca-Romero, Nicolás Quesada
Recently, Zhong et al. [1, 2] performed landmark Gaussian boson sampling experiments with up to 144 modes using threshold detectors. The authors claim to have achieved quantum computational advantage with the implementation of these experiments, named Jiuzhang 1.0 and Jiuzhang 2.0. Their experimental results are validated against several classical hypotheses and adversaries using tests such as the
-
Identifying Pauli spin blockade using deep learning Quantum (IF 6.4) Pub Date : 2023-08-08 Jonas Schuff, Dominic T. Lennon, Simon Geyer, David L. Craig, Federico Fedele, Florian Vigneau, Leon C. Camenzind, Andreas V. Kuhlmann, G. Andrew D. Briggs, Dominik M. Zumbühl, Dino Sejdinovic, Natalia Ares
Pauli spin blockade (PSB) can be employed as a great resource for spin qubit initialisation and readout even at elevated temperatures but it can be difficult to identify. We present a machine learning algorithm capable of automatically identifying PSB using charge transport measurements. The scarcity of PSB data is circumvented by training the algorithm with simulated data and by using cross-device
-
Quantum-assisted Monte Carlo algorithms for fermions Quantum (IF 6.4) Pub Date : 2023-08-03 Xiaosi Xu, Ying Li
Quantum computing is a promising way to systematically solve the longstanding computational problem, the ground state of a many-body fermion system. Many efforts have been made to realise certain forms of quantum advantage in this problem, for instance, the development of variational quantum algorithms. A recent work by Huggins et al. [1] reports a novel candidate, i.e. a quantum-classical hybrid Monte
-
Molecular Quantum Circuit Design: A Graph-Based Approach Quantum (IF 6.4) Pub Date : 2023-08-03 Jakob S. Kottmann
Science is rich in abstract concepts that capture complex processes in astonishingly simple ways. A prominent example is the reduction of molecules to simple graphs. This work introduces a design principle for parametrized quantum circuits based on chemical graphs, providing a way forward in three major obstacles in quantum circuit design for molecular systems: Operator ordering, parameter initialization
-
The meaning of redundancy and consensus in quantum objectivity Quantum (IF 6.4) Pub Date : 2023-08-03 Dario A. Chisholm, Luca Innocenti, G. Massimo Palma
While the terms "redundancy" and "consensus" are often used as synonyms in the context of quantum objectivity, we show here that these should be understood as two related but distinct notions, that quantify different features of the quantum-to-classical transition. We show that the two main frameworks used to measure quantum objectivity, namely spectrum broadcast structure and quantum Darwinism, are
-
20-Mode Universal Quantum Photonic Processor Quantum (IF 6.4) Pub Date : 2023-08-01 Caterina Taballione, Malaquias Correa Anguita, Michiel de Goede, Pim Venderbosch, Ben Kassenberg, Henk Snijders, Narasimhan Kannan, Ward L. Vleeshouwers, Devin Smith, Jörn P. Epping, Reinier van der Meer, Pepijn W. H. Pinkse, Hans van den Vlekkert, Jelmer J. Renema
Integrated photonics is an essential technology for optical quantum computing. Universal, phase-stable, reconfigurable multimode interferometers (quantum photonic processors) enable manipulation of photonic quantum states and are one of the main components of photonic quantum computers in various architectures. In this paper, we report the realization of the largest quantum photonic processor to date
-
Bell-type inequalities for systems of relativistic vector bosons Quantum (IF 6.4) Pub Date : 2023-07-27 Alan J. Barr, Paweł Caban, Jakub Rembieliński
We perform a detailed analysis of the possible violation of various Bell-type inequalities for systems of vector boson-antiboson pairs. Considering the general case of an overall scalar state of the bipartite system, we identify two distinct classes of such states, and determine the joint probabilities of spin measurement outcomes for each them. We calculate the expectation values of the CHSH, Mermin
-
Well-conditioned multi-product formulas for hardware-friendly Hamiltonian simulation Quantum (IF 6.4) Pub Date : 2023-07-25 Almudena Carrera Vazquez, Daniel J. Egger, David Ochsner, Stefan Woerner
Simulating the time-evolution of a Hamiltonian is one of the most promising applications of quantum computers. Multi-Product Formulas (MPFs) are well suited to replace standard product formulas since they scale better with respect to time and approximation errors. Hamiltonian simulation with MPFs was first proposed in a fully quantum setting using a linear combination of unitaries. Here, we analyze
-
Quantum-Classical Hybrid Systems and their Quasifree Transformations Quantum (IF 6.4) Pub Date : 2023-07-26 Lars Dammeier, Reinhard F. Werner
We study continuous variable systems, in which quantum and classical degrees of freedom are combined and treated on the same footing. Thus all systems, including the inputs or outputs to a channel, may be quantum-classical hybrids. This allows a unified treatment of a large variety of quantum operations involving measurements or dependence on classical parameters. The basic variables are given by canonical
-
Limitations of the Macaulay matrix approach for using the HHL algorithm to solve multivariate polynomial systems Quantum (IF 6.4) Pub Date : 2023-07-26 Jintai Ding, Vlad Gheorghiu, András Gilyén, Sean Hallgren, Jianqiang Li
Recently Chen and Gao [15] proposed a new quantum algorithm for Boolean polynomial system solving, motivated by the cryptanalysis of some post-quantum cryptosystems. The key idea of their approach is to apply a Quantum Linear System (QLS) algorithm to a Macaulay linear system over $\mathbb{C}$, which is derived from the Boolean polynomial system. The efficiency of their algorithm depends on the condition
-
Quantum Network Discrimination Quantum (IF 6.4) Pub Date : 2023-07-25 Christoph Hirche
Discrimination between objects, in particular quantum states, is one of the most fundamental tasks in (quantum) information theory. Recent years have seen significant progress towards extending the framework to point-to-point quantum channels. However, with technological progress the focus of the field is shifting to more complex structures: Quantum networks. In contrast to channels, networks allow
-
Adaptive surface code for quantum error correction in the presence of temporary or permanent defects Quantum (IF 6.4) Pub Date : 2023-07-25 Adam Siegel, Armands Strikis, Thomas Flatters, Simon Benjamin
Whether it is at the fabrication stage or during the course of the quantum computation, e.g. because of high-energy events like cosmic rays, the qubits constituting an error correcting code may be rendered inoperable. Such defects may correspond to individual qubits or to clusters and could potentially disrupt the code sufficiently to generate logical errors. In this paper, we explore a novel $adaptive$
-
Real-Time Krylov Theory for Quantum Computing Algorithms Quantum (IF 6.4) Pub Date : 2023-07-25 Yizhi Shen, Katherine Klymko, James Sud, David B. Williams-Young, Wibe A. de Jong, Norm M. Tubman
Quantum computers provide new avenues to access ground and excited state properties of systems otherwise difficult to simulate on classical hardware. New approaches using subspaces generated by real-time evolution have shown efficiency in extracting eigenstate information, but the full capabilities of such approaches are still not understood. In recent work, we developed the variational quantum phase
-
Chiral superconductivity in the doped triangular-lattice Fermi-Hubbard model in two dimensions Quantum (IF 6.4) Pub Date : 2023-07-20 Vinicius Zampronio, Tommaso Macrì
The triangular-lattice Fermi-Hubbard model has been extensively investigated in the literature due to its connection to chiral spin states and unconventional superconductivity. Previous simulations of the ground state of the doped system rely on quasi-one-dimensional lattices where true long-range order is forbidden. Here we simulate two-dimensional and quasi-one-dimensional triangular lattices using
-
MQT Bench: Benchmarking Software and Design Automation Tools for Quantum Computing Quantum (IF 6.4) Pub Date : 2023-07-20 Nils Quetschlich, Lukas Burgholzer, Robert Wille
Quantum software tools for a wide variety of design tasks on and across different levels of abstraction are crucial in order to eventually realize useful quantum applications. This requires practical and relevant benchmarks for new software tools to be empirically evaluated and compared to the current state of the art. Although benchmarks for specific design tasks are commonly available, the demand
-
Quantum computing Floquet energy spectra Quantum (IF 6.4) Pub Date : 2023-07-20 Benedikt Fauseweh, Jian-Xin Zhu
Quantum systems can be dynamically controlled using time-periodic external fields, leading to the concept of Floquet engineering, with promising technological applications. Computing Floquet energy spectra is harder than only computing ground state properties or single time-dependent trajectories, and scales exponentially with the Hilbert space dimension. Especially for strongly correlated systems
-
Volumetric Benchmarking of Error Mitigation with Qermit Quantum (IF 6.4) Pub Date : 2023-07-13 Cristina Cirstoiu, Silas Dilkes, Daniel Mills, Seyon Sivarajah, Ross Duncan
The detrimental effect of noise accumulates as quantum computers grow in size. In the case where devices are too small or noisy to perform error correction, error mitigation may be used. Error mitigation does not increase the fidelity of quantum states, but instead aims to reduce the approximation error in quantities of concern, such as expectation values of observables. However, it is as yet unclear
-
The battle of clean and dirty qubits in the era of partial error correction Quantum (IF 6.4) Pub Date : 2023-07-13 Daniel Bultrini, Samson Wang, Piotr Czarnik, Max Hunter Gordon, M. Cerezo, Patrick J. Coles, Lukasz Cincio
When error correction becomes possible it will be necessary to dedicate a large number of physical qubits to each logical qubit. Error correction allows for deeper circuits to be run, but each additional physical qubit can potentially contribute an exponential increase in computational space, so there is a trade-off between using qubits for error correction or using them as noisy qubits. In this work
-
On Hitting Times for General Quantum Markov Processes Quantum (IF 6.4) Pub Date : 2023-07-12 Lorenzo Laneve, Francesco Tacchino, Ivano Tavernelli
Random walks (or Markov chains) are models extensively used in theoretical computer science. Several tools, including analysis of quantities such as hitting and mixing times, are helpful for devising randomized algorithms. A notable example is Schöning's algorithm for the satisfiability (SAT) problem. In this work, we use the density-matrix formalism to define a $\textit{quantum Markov chain}$ model
-
Quantum Goemans-Williamson Algorithm with the Hadamard Test and Approximate Amplitude Constraints Quantum (IF 6.4) Pub Date : 2023-07-12 Taylor L. Patti, Jean Kossaifi, Anima Anandkumar, Susanne F. Yelin
Semidefinite programs are optimization methods with a wide array of applications, such as approximating difficult combinatorial problems. One such semidefinite program is the Goemans-Williamson algorithm, a popular integer relaxation technique. We introduce a variational quantum algorithm for the Goemans-Williamson algorithm that uses only $n{+}1$ qubits, a constant number of circuit preparations,
-
A scalable and fast artificial neural network syndrome decoder for surface codes Quantum (IF 6.4) Pub Date : 2023-07-12 Spiro Gicev, Lloyd C. L. Hollenberg, Muhammad Usman
Surface code error correction offers a highly promising pathway to achieve scalable fault-tolerant quantum computing. When operated as stabilizer codes, surface code computations consist of a syndrome decoding step where measured stabilizer operators are used to determine appropriate corrections for errors in physical qubits. Decoding algorithms have undergone substantial development, with recent work