arXiv subjects

H. L. Nourse

Publications and source records attributed to H. L. Nourse.

9 recordsLinked to original sources

arXiv2025

Equilibration of Non-interacting Photons and Quantum Signatures of Chaos

Equilibration plays a fundamental role in our understanding of statistical mechanics and the long-time dynamics of many-body systems. In quantum systems, the route to equilibration is intimately related to level repulsion and quantum signatures of chaos that are encoded in their unitary evolution. Chaotic quantum systems exhibit the level statistics characteristic of ensembles of random matrices. In this work, we demonstrate that single-particle chaos leads to equilibration of many non-interacting photons. We show that the underlying mechanisms for equilibration are operator spreading and quantum interference. More specifically, we demonstrate that the unitary dynamics of a general Floquet system implemented using single-mode phase shifters and multiport beamsplitters leads to equilibration of photons. We propose a realistic photonic implementation of the multiparticle kicked rotor, which is a Floquet system that we use as a concrete example of our general approach.

quant-ph↗

arXiv2025

Quantum simulation of thermodynamics: Maxwell relations for pair correlations

Quantum simulators hold enormous promise for advancing the modelling of materials and understanding emergent physics, such as high temperature superconductivity and topological order. While correlation functions are, typically, straightforward to measure in quantum simulators, thermodynamic properties are not. This limits our ability to directly compare the results of quantum simulations to experiments on the materials being modelled. Maxwell relations are an extremely powerful tool for characterising complex materials, as they enable the determination of challenging-to-measure thermodynamic properties from more accessible ones. Here, we introduce generalised Maxwell relations that relate every thermodynamic quantity to a single local correlation function. We illustrate their utility by deducing the thermodynamic properties of several iconic quantum many-body models from pair correlation functions using the generalised Maxwell relations. We show that this {universal} approach is readily accessible in quantum simulators and suggest applications to condensed matter systems where thermodynamic measurements are challenging, such as atomically thin materials.

quant-ph↗

arXiv2025

Experimental Quantum Simulation of Chemical Dynamics

Accurate simulation of dynamical processes in molecules and reactions is among the most challenging problems in quantum chemistry. Quantum computers promise efficient chemical simulation, but the existing quantum algorithms require many logical qubits and gates, placing practical applications beyond existing technology. Here, we carry out the first quantum simulations of chemical dynamics by employing a more hardware-efficient encoding scheme that uses both qubits and bosonic degrees of freedom. Our trapped-ion device accurately simulates the dynamics of non-adiabatic chemical processes, which are among the most difficult problems in computational chemistry because they involve strong coupling between electronic and nuclear motions. We demonstrate the programmability and versatility of our approach by simulating the dynamics of three different molecules as well as open-system dynamics in the condensed phase, all with the same quantum resources. Our approach requires orders of magnitude fewer resources than equivalent qubit-only quantum simulations, demonstrating the potential of using hybrid encoding schemes to accelerate quantum simulations of complex chemical processes, which could have applications in fields ranging from energy conversion and storage to biology and drug design.

quant-ph↗

arXiv2024

Flat bands and unconventional superconductivity in a simple model of metal-organic frameworks

The superconducting metal-organic framework Cu-BHT forms a kagome lattice with metals at the vertices and ligands along the bonds. This bipartite motif is common in reticular materials. We show that a tight-binding model on this lattice yields partially occupied interference-induced flat bands at half-filling with large gaps between them and all other bands. Long-range hopping induces curvature in the bands but leaves them flatter and more isolated than those in twisted bilayer graphene. The slave boson theory of the t-J model on this lattice shows highly unconventional superconductivity including an f -wave singlet phase. Thus, framework materials provide an ideal lattice-driven approach to strongly correlated phenomena in flat bands at high electronic densities.

cond-mat.supr-con↗

arXiv2024

Raman scattering signatures of spinons and triplons in frustrated antiferromagnets

Magnetically frustrated spin systems compose a significant proportion of topological quantum spin liquid candidates. Evidence for spin liquids in these materials comes largely from the detection of fractionalised spin-1/2 quasiparticles, known as spinons. However, the one-dimensional Heisenberg chain, which is topologically trivial, also hosts spinons. Thus, observing spinons does not necessarily signify long-range entanglement. Here, we show that spinons arising from one-dimensional physics leave a clear fingerprint in magnetic Raman scattering. We achieve this by calculating the magnetic Raman intensity of coupled Heisenberg chains. Our findings are in excellent agreement with the magnetic Raman scattering measurements on the anisotropic triangular antiferromagnet Ca$_3$ReO$_5$Cl$_2$.

cond-mat.str-el↗

arXiv2022

$C_3$ symmetry breaking metal-insulator transitions in a flat band in the half-filled Hubbard model on the decorated honeycomb lattice

We study the single-orbital Hubbard model on the half-filled decorated honeycomb lattice. In the non-interacting theory at half-filling the Fermi energy lies within a flat band where strong correlations are enhanced. The lattice is highly frustrated. We find a correlation driven first-order metal-insulator transition to two different insulating ground states - a dimer valence bond solid Mott insulator when inter-triangle correlations dominate, and a broken $\mathcal{C}_3$-symmetry antiferromagnet that arises from frustration when intra-triangle correlations dominate. The metal-insulator transitions into these two phases have very different characters. The metal-broken $\mathcal{C}_3$ antiferromagnetic transition is driven by spontaneous $\mathcal{C}_3$ symmetry breaking that lifts the topologically required degeneracy at the Fermi energy and opens an energy gap in the quasiparticle spectrum. The metal-dimer valence bond solid transition breaks no symmetries of the Hamiltonian. It is caused by strong correlations renormalizing the electronic structure into a phase that is adiabatically connected to both the trivial band insulator and the ground state of the spin-1/2 Heisenberg model in the relevant parameter regime. Therefore, neither of these metal-insulator transitions can be understood in either the Brinkmann-Rice or Slater paradigms.

cond-mat.str-el↗

arXiv2021

Spin-$0$ Mott insulator to metal to spin-$1$ Mott insulator transition in the single-orbital Hubbard model on the decorated honeycomb lattice

We study the interplay of strong electron correlations and intra-triangle spin exchange at two-thirds filling of the single-orbital Hubbard model on the decorated honeycomb lattice using rotationally invariant slave bosons. We find that the spin exchange tunes between a spin-$1$ Mott insulator, a metal, and a spin-$0$ Mott insulator when the exchange is antiferromagnetic. The Mott insulators occur from effective intra-triangle multi-orbital interactions and are adiabatically connected to the ground state of an isolated triangle. An antiferromagnetic spin exchange, as determined by the Goodenough-Kanamori rules, may occur in coordination polymers from kinetic exchange via the ligands. We characterize the magnetism in the regime where spin-triplets dominate. For small $U$ a spin-$1$ Slater insulator occurs with antiferromagnetic order between triangles. Magnetism in the spin-$1$ Mott insulator is described by a spin-$1$ Heisenberg model on a honeycomb lattice, whose ground state is Néel ordered.

cond-mat.str-el↗

arXiv2021

Multiple insulating phases due to the interplay of strong correlations and lattice geometry in a single-orbital Hubbard model

We report ten ground states arising from strong correlations in the single-orbital Hubbard model on the decorated honeycomb lattice; including Dirac metals, flat-band ferromagnets, real-space Mott insulators, dimer and trimer Mott insulators, and a spin-$1$ Mott insulator. The rich phase diagram arises from structures within the unit cell. Hence, such states are absent on simpler lattices. We argue that such insulating phases are prevalent on decorated lattices. These are found in many materials and common in coordination polymers, providing a playground to explore this physics.

cond-mat.str-el↗

arXiv2016

Haldane insulator protected by reflection symmetry in the doped Hubbard model on the three-legged ladder

We demonstrate the existence of an insulating phase in the three-legged Hubbard ladder at two-thirds filling. In this phase chargons are bound because the physics within a unit cell favors the formation of triplets. The resultant moments lead to a ground state in the Haldane phase, a symmetry protected topological state of matter. In this purely fermionic model, reflection is protecting but time reversal and dihedral symmetries are not, in contrast to spin models.

cond-mat.str-el↗