18 research outputs found
Quantum walks and Dirac cellular automata on a programmable trapped-ion quantum computer
The quantum walk formalism is a widely used and highly successful framework
for modeling quantum systems, such as simulations of the Dirac equation,
different dynamics in both the low and high energy regime, and for developing a
wide range of quantum algorithms. Here we present the circuit-based
implementation of a discrete-time quantum walk in position space on a
five-qubit trapped-ion quantum processor. We encode the space of walker
positions in particular multi-qubit states and program the system to operate
with different quantum walk parameters, experimentally realizing a Dirac
cellular automaton with tunable mass parameter. The quantum walk circuits and
position state mapping scale favorably to a larger model and physical systems,
allowing the implementation of any algorithm based on discrete-time quantum
walks algorithm and the dynamics associated with the discretized version of the
Dirac equation.Comment: 8 pages, 6 figure
Inference-Based Quantum Sensing
In a standard Quantum Sensing (QS) task one aims at estimating an unknown
parameter , encoded into an -qubit probe state, via measurements of
the system. The success of this task hinges on the ability to correlate changes
in the parameter to changes in the system response (i.e.,
changes in the measurement outcomes). For simple cases the form of
is known, but the same cannot be said for realistic
scenarios, as no general closed-form expression exists. In this work we present
an inference-based scheme for QS. We show that, for a general class of unitary
families of encoding, can be fully characterized by only
measuring the system response at parameters. In turn, this allows us to
infer the value of an unknown parameter given the measured response, as well as
to determine the sensitivity of the sensing scheme, which characterizes its
overall performance. We show that inference error is, with high probability,
smaller than , if one measures the system response with a number of
shots that scales only as . Furthermore, the
framework presented can be broadly applied as it remains valid for arbitrary
probe states and measurement schemes, and, even holds in the presence of
quantum noise. We also discuss how to extend our results beyond unitary
families. Finally, to showcase our method we implement it for a QS task on real
quantum hardware, and in numerical simulations.Comment: 5+10 pages, 3+5 figure
Para-particle oscillator simulations on a trapped ion quantum computer
Deformed oscillators allow for a generalization of the standard fermions and
bosons, namely, for the description of para-particles. Such particles, while
indiscernible in nature, can represent good candidates for descriptions of
physical phenomena like topological phases of matter. Here, we report the
digital quantum simulation of para-particle oscillators by mapping
para-particle states to the state of a qubit register, which allow us to
identify the para-particle oscillator Hamiltonian as an model, and further
digitize the system onto a universal set of gates. In both instances, the gate
depth grows polynomially with the number of qubits used. To establish the
validity of our results, we experimentally simulate the dynamics of
para-fermions and para-bosons, demonstrating full control of para-particle
oscillators on a quantum computer. Furthermore, we compare the overall
performance of the digital simulation of dynamics of the driven para-Fermi
oscillator to a recent analog quantum simulation result.Comment: 7 pages, 5 figures, 1 tabl