Article
Physics, Multidisciplinary
Matteo Ippoliti, Michael J. Gullans, Sarang Gopalakrishnan, David A. Huse, Vedika Khemani
Summary: The article explores the entanglement phase transition that unitary circuits can undergo with repeated projective measurements. Surprisingly, it is found that entanglement phase transitions can occur even in the absence of scrambling unitary dynamics, being primarily driven by measurements. The main driving force behind these transitions is the frustration caused by the mutual incompatibility of the measurements.
Article
Physics, Multidisciplinary
Roeland Wiersema, Cunlu Zhou, Juan Felipe Carrasquilla, Yong Baek Kim
Summary: Variational quantum algorithms (VQAs) optimize a parametrized quantum circuit classically to solve computational tasks and have the potential to improve our understanding of quantum many-body systems and advance machine learning algorithms on near-term quantum computers. However, a major challenge is controlling quantum entanglement and gradients during classical optimization. Inspired by recent studies, we investigate the entanglement transition in variational quantum circuits with intermediate projective measurements. We observe a measurement-induced entanglement transition from volume-law to area-law and find evidence that it belongs to the same universality class as random unitary circuits. Importantly, this transition aligns with a landscape transition from severe to mild/no barren plateaus in classical optimization, offering a new approach to improve the trainability of quantum circuits.
Article
Multidisciplinary Sciences
Hossein Dehghani, Ali Lavasani, Mohammad Hafezi, Michael J. Gullans
Summary: Measurement-induced entanglement phase transitions in monitored quantum systems can now be probed via entangling reference qubits and studying their purification dynamics. A neural network decoder is devised to determine the state of the reference qubits based on measurement outcomes, showing a change in the decoder's learnability during the entanglement phase transition. This method can be used to detect entanglement phase transitions in experiments and extract critical exponents.
NATURE COMMUNICATIONS
(2023)
Article
Materials Science, Multidisciplinary
Alberto D. Verga
Summary: Investigated the Floquet dynamics of the cluster spin chain in the presence of an external field and particle interaction, exploring the entanglement properties of the topological and magnetic phases. Identified dynamical phase transitions between low- and high-entanglement nonthermal states, accompanied by the emergence of magnetic order.
Article
Multidisciplinary Sciences
Avikar Periwal, Eric S. Cooper, Philipp Kunkel, Julian F. Wienand, Emily J. Davis, Monika Schleier-Smith
Summary: Interactions play a crucial role in controlling the flow of information and creating correlations in many-body quantum systems. By programming non-local interactions in an array of atomic ensembles within an optical cavity, researchers have been able to access effective geometries with different dimensions and topologies than the physical geometry of the array. This work has implications for simulating frustrated magnets, investigating quantum optimization paradigms, and engineering entangled resource states for sensing and computation.
Article
Materials Science, Multidisciplinary
Satoru Hayami
Summary: The theoretical investigation reveals that a skyrmion crystal (SkX) can be realized in frustrated triangular magnets with easy-plane single-ion anisotropy by applying an in-plane magnetic field. In addition to SkX, multiple-Q states are also stabilized in the presence of easy-plane anisotropy. This study provides a new possibility to explore SkX in easy-plane frustrated magnets.
Article
Quantum Science & Technology
R. Muthuganesan, V. K. Chandrasekar
Summary: The dynamics of entanglement and measurement-induced nonlocality in a system of two interacting spin-1/2 qubits with intrinsic decoherence were studied under different initial conditions. It was found that the robustness and generation of quantum correlations depend on physical parameters for both pure and separable initial states. Despite phase decoherence, all correlations reach steady state values after exhibiting oscillations, showing that the enhancement of correlations may occur by adjusting the strength of the Dzyaloshinskii-Moriya interaction. Intervention of the magnetic field was found to decrease quantum correlations, and quantum correlations were also observed in unentangled states.
QUANTUM INFORMATION PROCESSING
(2021)
Article
Physics, Multidisciplinary
Crystal Noel, Pradeep Niroula, Daiwei Zhu, Andrew Risinger, Laird Egan, Debopriyo Biswas, Marko Cetina, Alexey V. Gorshkov, Michael J. Gullans, David A. Huse, Christopher Monroe
Summary: This study investigates the purification phase transition using random quantum circuits implemented on a trapped-ion quantum computer. Experimental evidence of two phases is found, and numerical calculations demonstrate the emergence of critical properties of the transition.
Article
Physics, Fluids & Plasmas
Yi-Cheng Zhao, Hao-Wei Hu, I Lin
Summary: The disorder-order transitions of layering and intralayer structural orders in three-dimensional Yukawa liquids under enhanced confinement effect were investigated numerically. It was found that with decreasing normal distance to the confinement boundary, the emergence of small clusters of layering order (LOS) is followed by the formation of large percolating LOS clusters spanning the system. The disorder-order transition of intraslab structural ordering exhibits a similar generic behavior as layering. The correlation between local layering order and local intralayer structural order gradually increases as the percolating transition slab is approached.
Article
Physics, Multidisciplinary
Shutong Li, Turan Birol
Summary: This study demonstrates that electron doping can enhance oxygen octahedral rotations in certain hybrid-improper ferroelectrics, thereby strengthening structural polarization. Using this design strategy, a cation ordered Ruddlesden-Popper compound has been predicted to be driven into a metallic ferroelectric-like phase via electrolyte gating.
PHYSICAL REVIEW LETTERS
(2021)
Article
Physics, Multidisciplinary
Xiangyi Meng, Jianxi Gao, Shlomo Havlin
Summary: The new statistical theory, concurrence percolation theory (ConPT), is similar to classical percolation but fundamentally different, built by generalizing bond percolation in terms of sponge-crossing paths instead of clusters. The entanglement transmission threshold predicted by ConPT is lower than the known classical-percolation-based results and is readily achievable on any series-parallel networks such as the Bethe lattice. ConPT promotes our understanding of how well quantum communication can be further systematically improved versus classical statistical predictions under the limitation of QN locality, offering a more general and efficient quantum advantage.
PHYSICAL REVIEW LETTERS
(2021)
Article
Physics, Applied
Jinzhao Sun, Xiao Yuan, Takahiro Tsunoda, Vlatko Vedral, Simon C. Benjamin, Suguru Endo
Summary: Quantum error mitigation is crucial for NISQ devices, and a stochastic QEM method is proposed to effectively suppress noise, applicable to both digital quantum computers and simulators. Numerical tests demonstrate an improvement in simulation accuracy under various conditions.
PHYSICAL REVIEW APPLIED
(2021)
Article
Physics, Multidisciplinary
M. Libersky, R. D. McKenzie, D. M. Silevitch, P. C. E. Stamp, T. F. Rosenbaum
Summary: In this study, low-energy excitation modes of the quantum Ising magnet LiHoF4 were directly measured using microwave spectroscopy. It was found that a set of collective electronuclear modes exist, where the spin-1/2 Ising electronic spins hybridize with spin-7/2 Ho nuclear spins. The lowest-lying electronuclear mode softens near the quantum critical point, but this softening is rapidly quenched by a longitudinal magnetic field. Similar electronuclear structures are expected to be present in other spin-based quantum Ising systems.
PHYSICAL REVIEW LETTERS
(2021)
Article
Physics, Multidisciplinary
T. Mueller, S. Diehl, M. Buchhold
Summary: We have identified an unconventional algebraic scaling phase in the quantum dynamics of long-range hopping free fermions under continuous local measurements. This phase exhibits features such as algebraic entanglement entropy growth and a slow algebraic decay of the density-density correlation function.
PHYSICAL REVIEW LETTERS
(2022)
Article
Physics, Multidisciplinary
Piotr Sierant, Xhek Turkeshi
Summary: Many-body unitary dynamics with repeated measurements can exhibit measurement-induced phase transitions. We study the entanglement entropy behavior at the absorbing state phase transition by employing feedback-control operations to steer the dynamics towards an absorbing state. We observe distinct subextensive scalings of entanglement entropy for short-range control operations and a transition between volume-law and area-law phases for long-range feedback operations. The fluctuations of entanglement entropy and the order parameter of the absorbing state transition are fully coupled for strongly entangling feedback operations.
PHYSICAL REVIEW LETTERS
(2023)
Article
Physics, Multidisciplinary
Adam Nahum, Jonathan Ruhman, Sagar Vijay, Jeongwan Haah
Article
Physics, Multidisciplinary
Adam Nahum, Sagar Vijay, Jeongwan Haah
Article
Physics, Multidisciplinary
G. J. Sreejith, Stephen Powell, Adam Nahum
PHYSICAL REVIEW LETTERS
(2019)
Article
Physics, Multidisciplinary
Tianci Zhou, Adam Nahum
Article
Physics, Multidisciplinary
Zongping Gong, Adam Nahum, Lorenzo Piroli
Summary: In two-dimensional Floquet systems, many-body localized dynamics in the bulk leads to chaotic evolution characterized by a nonzero chiral topological index at the one-dimensional edges. This anomalous dynamics is qualitatively different from local-Hamiltonian evolution. By analyzing solvable models of random quantum cellular automata, it is found that a nonzero index results in asymmetric butterfly velocities, different diffusive broadening of the light cones, and a modification of the order relations between the butterfly and entanglement velocities. These results can be understood by generalizing the entanglement membrane theory, considering a spacetime entropy current fixed by the index.
PHYSICAL REVIEW LETTERS
(2022)
Article
Physics, Multidisciplinary
Andres M. Somoza, Pablo Serna, Adam Nahum
Summary: The study investigates the self-dual transition of Z(2) gauge theory in 2 + 1D, revealing it to be a continuous transition with remarkable parameter-free scaling collapse. A general theory regarding 1-form symmetries and patching of membranes is proposed, connecting it to the percolation of anyon worldlines in spacetime. The results provide insights into the critical behavior of the system and suggest variations for further exploration.
Article
Materials Science, Multidisciplinary
Adam Nahum, Sthitadhi Roy, Sagar Vijay, Tianci Zhou
Summary: We study the real-time correlators of local operators in chaotic quantum many-body systems. These correlators exhibit universal structure at late times, determined by the geometry of the dominant operator-space Feynman trajectories. The decay of local correlations in the absence of conservation laws is described by rate functions associated with spacetime structures. In 1+1D, the operator histories can exhibit a phase transition, leading to singular behavior in the rate function. In higher-dimensional systems, thin trajectories always dominate. We also discuss the deducibility of butterfly velocity from time-ordered two-point functions and the computation of correlators in random circuits.
Article
Materials Science, Multidisciplinary
Adam Nahum
Summary: In this study, it is shown that the quantum spin impurity coupled to a gapless free field exhibits an annihilation between two nontrivial renormalization group fixed points at a critical value of the interaction exponent. This clarifies the phase diagram of the Bose-Kondo model and highlights its role as a toy model for fixed point annihilation and quasiuniversality in higher dimensions.
Article
Quantum Science & Technology
Adam Nahum, Sthitadhi Roy, Brian Skinner, Jonathan Ruhman
Summary: This work explores theoretical approaches to measurement-induced phase transitions and entanglement transitions in random tensor networks. Results are presented for all-to-all quantum circuits and spatially local systems of any finite dimensionality, with comparisons made between theory and numerics. Field theories are proposed for different phase transitions, with a surprising difference observed between the measurement phase transition and other cases. Variants of the measurement problem with additional structure, such as free-fermion structure, are also discussed for future research directions.
Article
Physics, Multidisciplinary
Zhehao Dai, Adam Nahum
PHYSICAL REVIEW RESEARCH
(2020)
Article
Physics, Multidisciplinary
Adam Nahum, Brian Skinner
PHYSICAL REVIEW RESEARCH
(2020)
Article
Materials Science, Multidisciplinary
Tianci Zhou, Adam Nahum
Article
Materials Science, Multidisciplinary
Vedika Khemani, David A. Huse, Adam Nahum
Article
Materials Science, Multidisciplinary
Adam Nahum, Jonathan Ruhman, David A. Huse