2024 New's Items

Entanglement dynamics in monitored Kitaev circuits: loop models, symmetry classification, and quantum Lifshitz scaling

Klocke, K.
Simm, D.
Zhu, G.-Y.
Trebst, S.
Buchhold, M.
2024

Quantum circuits offer a versatile platform for simulating digital quantum dynamics and uncovering novel states of non-equilibrium quantum matter. One principal example are measurement-induced phase transitions arising from non-unitary dynamics in monitored circuits, which employ mid-circuit measurements as an essential building block next to standard unitary gates. Although a comprehensive understanding of the dynamics in generic circuits is still evolving, we contend that monitored quantum circuits give rise to robust phases of dynamic matter, which – akin to Hamiltonian ground state...

Spin Excitation Continuum in the Exactly Solvable Triangular-Lattice Spin Liquid CeMgAl11O19

Gao, B.
Chen, T.
Liu, C.
Klemm, M. L.
Zhang, S.
Ma, Z.
Xu, X.
Won, C.
McCandless, G. T.
Murai, N.
Ohira-Kawamura, S.
Moxim, S. J.
Ryan, J. T.
Huang, X.
Wang, X.
Chan, J. Y.
Cheong, S.-W.
Tchernyshyov, O.
Balents, L.
Dai, P.
2024

In magnetically ordered insulators, elementary quasiparticles manifest as spin waves - collective motions of localized magnetic moments propagating through the lattice - observed via inelastic neutron scattering. In effective spin-1/2 systems where geometric frustrations suppress static magnetic order, spin excitation continua can emerge, either from degenerate classical spin ground states or from entangled quantum spins characterized by emergent gauge fields and deconfined fractionalized excitations. Comparing the spin Hamiltonian with theoretical models can unveil the microscopic...

Sublattice polarization from destructive interference on common lattices

Yu-Ping Lin
2024
We show that sublattice-polarized states (SLPSs) appear ubiquitously on the common lattices. We first establish the destructive-interference (DI) scenario for the SLPSs, which is systematized by a point-group-symmetry interpretation. The examples on common one-, two-, and three-dimensional lattices are then demonstrated. We also deduce the symmetry-protected robustness of SLPSs against further-neighbor hoppings. Moreover, the DI scenario can be generalized to the multi-SLP. The important effects on interaction-driven phases are studied by Hartree-Fock analysis.

A tale of two localizations: coexistence of flat bands and Anderson localization in a photonics-inspired amorphous system

Dresselhaus, E. J.
Avdoshkin, A.
Jia, Z.
Secli, M.
Kante, B.
Moore, J. E.
2024
Emerging experimental platforms use amorphousness, a constrained form of disorder, to tailor meta-material properties. We study localization under this type of disorder in a class of models generalizing recent experiments on photonic systems. We explore two kinds of localization that emerge in these models: Anderson localization by disorder, and the existence of compact, macroscopically degenerate localized states as in many crystalline flat bands. We find localization properties to depend on the symmetry class within a family of amorphized kagom\'{e} tight-binding models, set by a tunable...

Machine learning of 27Al NMR quadrupolar tensors for crystalline structures from DFT

Sun, H.
Dwaraknath, S.
West, M. E.
Ling, H.
Persson, K.
Hayes, S.
2024
NMR crystallography has emerged as promising technique for the determination and refinement of crystal structures. The crystal structure of compounds containing quadrupolar nuclei, such as 27Al, can be improved by directly comparing solid-state NMR measurements to DFT computations of the electric field gradient (EFG). The high computational cost of these first-principles calculations limits the applicability of this method to all but the most well-defined structures. We developed a fast, low-cost machine learning model to predict EFG parameters based on local structural motifs and elemental...

Quantum Melting of a Disordered Wigner Solid

Xiang, Z.
Li, H.
Xiao, J.
Naik, M. H.
Ge, Z.
He, Z.
Chen, S.
Nie, J.
Li, S.
Jiang, Y.
Sailus, R.
Banerjee, R.
Taniguchi, T.
Watanabe, K.
Tongay, S.
Louie, S. G.
Crommie, M. F.
Wang, F.
2024

The behavior of two-dimensional electron gas (2DEG) in extreme coupling limits are reasonably well-understood, but our understanding of intermediate region remains limited. Strongly interacting electrons crystalize into a solid phase known as the Wigner crystal at very low densities, and these evolve to a Fermi liquid at high densities. At intermediate densities, however, where the Wigner crystal melts into a strongly correlated electron fluid that is poorly understood partly due to a lack of microscopic probes for delicate quantum phases. Here we report the first imaging of a...

An efficient quantum algorithm for generation of ab initio n-th order susceptibilities for non-linear spectroscopies

Kharazi, T.
Stetina, T. F.
Ko, L.
Low, G. H.
Whaley, K. B.
2024

We develop and analyze a fault-tolerant quantum algorithm for computing n-th order response properties necessary for analysis of non-linear spectroscopies of molecular and condensed phase systems. We use a semi-classical description in which the electronic degrees of freedom are treated quantum mechanically and the light is treated as a classical field. The algorithm we present can be viewed as an implementation of standard perturbation theory techniques, focused on ab initio calculation of n-th order response functions. We provide cost estimates in terms of the number of queries to the...

ML-Powered FPGA-based Real-Time Quantum State Discrimination Enabling Mid-circuit Measurements

Vora, N. R.
Xu, Y.
Hashim, A.
Fruitwala, N.
Nguyen, H. N.
Liao, H.
Balewski, J.
Rajagopala, A.
Nowrouzi, K.
Ji, Q.
Whaley, K. B.
Siddiqi, I.
Nguyen, P.
Huang, G.
2024

Similar to reading the transistor state in classical computers, identifying the quantum bit (qubit) state is a fundamental operation to translate quantum information. However, identifying the qubit state has been the slowest and most susceptible to errors operation on superconducting quantum processors. Most existing qubit state discriminating algorithms have only been implemented and optimized “after the fact”—using offline data transferred from a quantum control circuit to host computers. Real-time state discrimination is not possible because a superconducting qubit state only survives...

The surface chemistry of colloidal lead halide perovskite nanowires

Oddo, A. M.
Arnold, M.
Yang, P.
2024

This study explored the interplay between the ligand–surface chemistry of colloidal CsPbBr3 nanowires (NWs) and their optical properties. The ligand equilibrium was probed using nuclear magnetic resonance spectroscopy, and by perturbing the equilibrium via dilution, the gradual removal of ligands from the CsPbBr3 surface was observed. This removal was correlated with an increase in the surface defect density, as suggested by a broadening of the photoluminescence (PL) spectrum, a decrease in the PL quantum yield (PLQY), and quenching of...

Performance of wave function and Green's functions based methods for non equilibrium many-body dynamics

Reeves, C. C.
Harsha, G.
Shee, A.
Zhu, Y.
Blommel, T.
Yang, C.
Whaley, K. B.
Zgid, D.
Vlček, V.
2024

Theoretical descriptions of the non-equilibrium dynamics of quantum many-body systems essentially employ either (i) explicit treatments, relying on the truncation of the expansion of the many-body wavefunction, (ii) compressed representations of the many-body wavefunction, or (iii) evolution of an effective (downfolded) representation through Green’s functions. In this work, we select representative cases of each of the methods and address how these complementary approaches capture the dynamics driven by intense field perturbations to non-equilibrium states. Under strong driving, the...