Fernando Iniguez
Research Subjects
Fernando Iniguez has a total of 2 co-authors. Here are the top co-authors by number of shared publications:
- Mark Srednicki
Department of Physics University of California 93106 Santa Barbara CA
2 shared publications - Sean McBride
University of California
1 shared publication
Latest Publications
- Open Access
Microcanonical Truncations of Observables in Quantum Chaotic Systems
We consider the properties of an observable (such as a single spin component that squares to the identity) when expressed as a matrix in the basis of energy eigenstates, and then truncated to a microcanonical slice of energies of varying width. For a quantum chaotic system, we model the unitary or orthogonal matrix that relates the spin basis to the energy basis as a random matrix selected from the appropriate Haar measure. We find that the spectrum of eigenvalues is given by a centered Jacobi distribution that approaches the Wigner semicircle of a random hermitian matrix for small slices. For slices that contain more than half the states, there is a set of eigenvalues of exactly $\pm 1$. The transition to this qualitatively different behavior at half size is similar to that seen in other quantities such as entanglement entropy. Our results serve as a benchmark model for numerical calculations in realistic physical systems.Open AccessMicrocanonical Truncations of Observables in Quantum Chaotic Systems
We consider the properties of an observable (such as a single spin component that squares to the identity) when expressed as a matrix in the basis of energy eigenstates, and then truncated to a microcanonical slice of energies of varying width. For a quantum chaotic system, we model the unitary or orthogonal matrix that relates the spin basis to the energy basis as a random matrix selected from the appropriate Haar measure. We find that the spectrum of eigenvalues is given by a centered Jacobi distribution that approaches the Wigner semicircle of a random hermitian matrix for small slices. For slices that contain more than half the states, there is a set of eigenvalues of exactly $\pm 1$. The transition to this qualitatively different behavior at half size is similar to that seen in other quantities such as entanglement entropy. Our results serve as a benchmark model for numerical calculations in realistic physical systems. - Open Access
Quantum Fisher Information for Different States and Processes in Quantum Chaotic Systems
The quantum Fisher information (QFI) associated with a particular process applied to a many-body quantum system has been suggested as a diagnostic for the nature of the system's quantum state, e.g., a thermal density matrix vs. a pure state in a system that obeys the eigenstate thermalization hypothesis (ETH). We compute the QFI for both an energy eigenstate and a thermal density matrix for a variety of processes in a system obeying ETH, including a change in the hamiltonian that is either sudden (a quench), slow (adiabatic), or followed by contact with a heat bath. We compare our results with earlier results for a local unitary transformation.
Open AccessQuantum Fisher Information for Different States and Processes in Quantum Chaotic Systems
The quantum Fisher information (QFI) associated with a particular process applied to a many-body quantum system has been suggested as a diagnostic for the nature of the system's quantum state, e.g., a thermal density matrix vs. a pure state in a system that obeys the eigenstate thermalization hypothesis (ETH). We compute the QFI for both an energy eigenstate and a thermal density matrix for a variety of processes in a system obeying ETH, including a change in the hamiltonian that is either sudden (a quench), slow (adiabatic), or followed by contact with a heat bath. We compare our results with earlier results for a local unitary transformation.
- Open Access
Entanglement Negativity Transitions in Chaotic Eigenstates
It was recently noted that the entanglement entropy for a subsystem of a chaotic eigenstate exhibits an enhanced correction when the subsystem approaches a phase transition at half the total system size. This enhanced correction was derived for general subsystems by Dong and Wang by summing over noncrossing permutations, which can be thought of as ``saddles'' either in a sum emerging from averaging over Wick contractions or in an analogous gravitational calculation. We extend these results to the case of entanglement negativity, an entanglement measure defined on a bipartite density matrix. We focus on a particular transition previously studied in a toy model of JT gravity, one for which the sum over permutations was found to give similar (or even stronger) enhanced corrections. We derive and resum the relevant permutations to give a form for the averaged negativity spectrum, reproducing the gravitational answer for some quantities and finding tension with other quantities, namely the partially transposed entropy. Along the way, we extend the results of Dong and Wang to the case of $n < 1$ Rényi entropy, showing that it always receives volume law corrections.Open AccessEntanglement Negativity Transitions in Chaotic Eigenstates
It was recently noted that the entanglement entropy for a subsystem of a chaotic eigenstate exhibits an enhanced correction when the subsystem approaches a phase transition at half the total system size. This enhanced correction was derived for general subsystems by Dong and Wang by summing over noncrossing permutations, which can be thought of as ``saddles'' either in a sum emerging from averaging over Wick contractions or in an analogous gravitational calculation. We extend these results to the case of entanglement negativity, an entanglement measure defined on a bipartite density matrix. We focus on a particular transition previously studied in a toy model of JT gravity, one for which the sum over permutations was found to give similar (or even stronger) enhanced corrections. We derive and resum the relevant permutations to give a form for the averaged negativity spectrum, reproducing the gravitational answer for some quantities and finding tension with other quantities, namely the partially transposed entropy. Along the way, we extend the results of Dong and Wang to the case of $n < 1$ Rényi entropy, showing that it always receives volume law corrections.