6 research outputs found
Improving quantum state detection with adaptive sequential observations
For many quantum systems intended for information processing, one detects the
logical state of a qubit by integrating a continuously observed quantity over
time. For example, ion and atom qubits are typically measured by driving a
cycling transition and counting the number of photons observed from the
resulting fluorescence. Instead of recording only the total observed count in a
fixed time interval, one can observe the photon arrival times and get a state
detection advantage by using the temporal structure in a model such as a Hidden
Markov Model. We study what further advantage may be achieved by applying
pulses to adaptively transform the state during the observation. We give a
three-state example where adaptively chosen transformations yield a clear
advantage, and we compare performances on an ion example, where we see
improvements in some regimes. We provide a software package that can be used
for exploration of temporally resolved strategies with and without adaptively
chosen transformations.Comment: Submitted for publication in Quantum Science and Technology. 26
pages, 8 figures. Corrected typos in appendix, updated acknowledgement
An atomic boson sampler
A boson sampler implements a restricted model of quantum computing. It is
defined by the ability to sample from the distribution resulting from the
interference of identical bosons propagating according to programmable,
non-interacting dynamics. Here, we demonstrate a new combination of tools for
implementing boson sampling using ultracold atoms in a two-dimensional,
tunnel-coupled optical lattice. These tools include fast and programmable
preparation of large ensembles of nearly identical bosonic atoms
( indistinguishability) by means of rearrangement with
optical tweezers and high-fidelity optical cooling, propagation for variable
evolution time in the lattice with low loss (, independent of
evolution time), and high fidelity detection of the atom positions after their
evolution (typically ). With this system, we study specific
instances of boson sampling involving up to atoms distributed among sites in the lattice. Direct verification of a given boson sampling
distribution is not feasible in this regime. Instead, we introduce and perform
targeted tests to determine the indistinguishability of the prepared atoms, to
characterize the applied family of single particle unitaries, and to observe
expected bunching features due to interference for a large range of atom
numbers. When extended to interacting systems, our work demonstrates the core
capabilities required to directly assemble ground and excited states in
simulations of various Hubbard models.Comment: 20 pages, 7 figures (main text and methods); 8 pages, 2 figures
(supplemental materials
High-fidelity indirect readout of trapped-ion hyperfine qubits
We propose and demonstrate a protocol for high-fidelity indirect readout of
trapped ion hyperfine qubits, where the state of a qubit ion is
mapped to a readout ion using laser-driven Raman
transitions. By partitioning the ground state hyperfine
manifold into two subspaces representing the two qubit states and choosing
appropriate laser parameters, the protocol can be made robust to spontaneous
photon scattering errors on the Raman transitions, enabling repetition for
increased readout fidelity. We demonstrate combined readout and back-action
errors for the two subspaces of and
with 68% confidence while avoiding decoherence
of spectator qubits due to stray resonant light that is inherent to direct
fluorescence detection.Comment: 7 + 6 pages, 3 + 1 figure
The Grizzly, January 28, 1991
Policies and Statistics, A Security Concern: New Quad Regulations; Crime Report Released • Sonia Sanchez: Poet for Peace • Gulf Dialogue Continues • Independence Dogs • Financial Aid Month • You Asked for it: You Got It!! • New Quad Policy • Presidency Symposium • When is Dr. Martin Luther King, Jr.\u27s Birthday? • Who\u27s Who Announced • Mission Conference Held • Back to the Basics • The Innocent • Swimmers on Win Streak • Women Hope for Good Things to Come • A Roller Coaster Season for the Hoopsters • Women Rounding-out Season • The Dream Lives On • Letter: Bundle Up! • Researchers Psyched Out • The Technology of War • A Wasted Solution?https://digitalcommons.ursinus.edu/grizzlynews/1268/thumbnail.jp