6 research outputs found
Validating phase-space methods with tensor networks in two-dimensional spin models with power-law interactions
Using a recently developed extension of the time-dependent variational
principle for matrix product states, we evaluate the dynamics of 2D power-law
interacting XXZ models, implementable in a variety of state-of-the-art
experimental platforms. We compute the spin squeezing as a measure of
correlations in the system, and compare to semiclassical phase-space
calculations utilizing the discrete truncated Wigner approximation (DTWA). We
find the latter efficiently and accurately captures the scaling of entanglement
with system size in these systems, despite the comparatively resource-intensive
tensor network representation of the dynamics. We also compare the steady-state
behavior of DTWA to thermal ensemble calculations with tensor networks. Our
results open a way to benchmark dynamical calculations for two-dimensional
quantum systems, and allow us to rigorously validate recent predictions for the
generation of scalable entangled resources for metrology in these systems.Comment: 6+4 pages, 3+1 figure
Enhancing spin squeezing using soft-core interactions
We propose a new protocol for preparing spin squeezed states in controllable
atomic, molecular, and optical systems, with particular relevance to emerging
optical clock platforms compatible with Rydberg interactions. By combining a
short-ranged, soft-core potential with an external drive, we can transform
naturally emerging Ising interactions into an XX spin model while opening a
many-body gap. The gap helps maintain the system within a collective manifold
of states where metrologically useful spin squeezing can be generated at a
level comparable to the spin squeezing generated in systems with genuine
all-to-all interactions. We examine the robustness of our protocol to
experimentally-relevant decoherence and show favorable performance over typical
protocols lacking gap protection.Comment: 5+4 pages, 3+3 figure
Fast generation of spin squeezing via resonant spin-boson coupling
We propose protocols for the creation of useful entangled states in a system
of spins collectively coupled to a bosonic mode, directly applicable to
trapped-ion and cavity QED setups. The protocols use coherent manipulations of
the spin-boson interactions naturally arising in these systems to prepare spin
squeezed states exponentially fast in time. We demonstrate the robustness of
the protocols by analyzing the effects of natural sources of decoherence in
these systems and show their advantage compared to more standard slower
approaches where entanglement is generated algebraically with time.Comment: 6 pages, 4 figures (18 pages, 8 figures with appendices
Comparison of Spontaneous Emission in Trapped Ion Multiqubit Gates at High Magnetic Fields
Penning traps have been used for performing quantum simulations and sensing
with hundreds of ions and provide a promising route toward scaling up trapped
ion quantum platforms because of the ability to trap and control up to
thousands of ions in 2D and 3D crystals. A leading source of decoherence in
laser-based multiqubit operations on trapped ions is off-resonant spontaneous
emission. While many trapped ion quantum computers or simulators utilize clock
qubits, other systems rely on Zeeman qubits, which require a more complex
calculation of this decoherence. We examine theoretically the impacts of
spontaneous emission on quantum gates performed with trapped ions in a high
magnetic field. We consider two types of gates -- light-shift and
Molmer-Sorensen gates -- and compare the decoherence errors in each. We also
compare different detunings, polarizations, and required intensities of the
laser beams used to drive the gates. We show that both gates can have similar
performance at their optimal operating conditions and examine the experimental
feasibility of various operating points. By examining the magnetic field
dependence of each gate, we demonstrate that when the state fine structure
splitting is large compared to the Zeeman splittings, the theoretical
performance of the Molmer-Sorensen gate is significantly better than that of
the light-shift gate. Additionally, for the light-shift gate, we make an
approximate comparison between the fidelities that can be achieved at high
fields with the fidelities of state-of-the-art two-qubit trapped ion quantum
gates. We show that, with regard to spontaneous emission, the achievable
infidelity of our current configuration is about an order of magnitude larger
than that of the best low-field gates, but we also discuss alternative
configurations with potential error rates that are comparable with
state-of-the-art trapped ion gates.Comment: Main text: 19 pages, 13 figures, Appendix: 7 pages, 1 figure, updated
to improve presentatio