71,345 research outputs found
Theoretical Design and FPGA-Based Implementation of Higher-Dimensional Digital Chaotic Systems
Traditionally, chaotic systems are built on the domain of infinite precision
in mathematics. However, the quantization is inevitable for any digital
devices, which causes dynamical degradation. To cope with this problem, many
methods were proposed, such as perturbing chaotic states and cascading multiple
chaotic systems. This paper aims at developing a novel methodology to design
the higher-dimensional digital chaotic systems (HDDCS) in the domain of finite
precision. The proposed system is based on the chaos generation strategy
controlled by random sequences. It is proven to satisfy the Devaney's
definition of chaos. Also, we calculate the Lyapunov exponents for HDDCS. The
application of HDDCS in image encryption is demonstrated via FPGA platform. As
each operation of HDDCS is executed in the same fixed precision, no
quantization loss occurs. Therefore, it provides a perfect solution to the
dynamical degradation of digital chaos.Comment: 12 page
Efficient Grover search with Rydberg blockade
We present efficient methods to implement the quantum computing Grover search
algorithm using the Rydberg blockade interaction. We show that simple pi-pulse
excitation sequences between ground and Rydberg excited states readily produce
the key conditional phase shift and inversion-about-the mean unitary operations
for the Grover search. Multi-qubit implementation schemes suitable for
different properties of the atomic interactions are identifed and the error
scaling of the protocols with system size is found to be promising for
immediate experimental investigation.Comment: Detailed description of algorithm for sub-register architecture.
Error budget modified for Cs atomic parameters. To appear in J. Phys. B.
Special Issue on Strong Rydberg interactions in ultracold atomic and
molecular gase
Robustness of high-fidelity Rydberg gates with single-site addressability
Controlled phase (CPHASE) gates can in principle be realized with trapped
neutral atoms by making use of the Rydberg blockade. Achieving the ultra-high
fidelities required for quantum computation with such Rydberg gates is however
compromised by experimental inaccuracies in pulse amplitudes and timings, as
well as by stray fields that cause fluctuations of the Rydberg levels. We
report here a comparative study of analytic and numerical pulse sequences for
the Rydberg CPHASE gate that specifically examines the robustness of the gate
fidelity with respect to such experimental perturbations. Analytical pulse
sequences of both simultaneous and stimulated Raman adiabatic passage (STIRAP)
are found to be at best moderately robust under these perturbations. In
contrast, optimal control theory is seen to allow generation of numerical
pulses that are inherently robust within a predefined tolerance window. The
resulting numerical pulse shapes display simple modulation patterns and their
spectra contain only one additional frequency beyond the basic resonant Rydberg
gate frequencies. Pulses of such low complexity should be experimentally
feasible, allowing gate fidelities of order 99.90 - 99.99% to be achievable
under realistic experimental conditions.Comment: 12 pages, 14 figure
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