12,368 research outputs found
A trapped single ion inside a Bose-Einstein condensate
Improved control of the motional and internal quantum states of ultracold
neutral atoms and ions has opened intriguing possibilities for quantum
simulation and quantum computation. Many-body effects have been explored with
hundreds of thousands of quantum-degenerate neutral atoms and coherent
light-matter interfaces have been built. Systems of single or a few trapped
ions have been used to demonstrate universal quantum computing algorithms and
to detect variations of fundamental constants in precision atomic clocks. Until
now, atomic quantum gases and single trapped ions have been treated separately
in experiments. Here we investigate whether they can be advantageously combined
into one hybrid system, by exploring the immersion of a single trapped ion into
a Bose-Einstein condensate of neutral atoms. We demonstrate independent control
over the two components within the hybrid system, study the fundamental
interaction processes and observe sympathetic cooling of the single ion by the
condensate. Our experiment calls for further research into the possibility of
using this technique for the continuous cooling of quantum computers. We also
anticipate that it will lead to explorations of entanglement in hybrid quantum
systems and to fundamental studies of the decoherence of a single, locally
controlled impurity particle coupled to a quantum environment
NOVEL RESOURCE EFFICIENT CIRCUIT DESIGNS FOR REBOOTING COMPUTING
CMOS based computing is reaching its limits. To take computation beyond Moores law (the number of transistors and hence processing power on a chip doubles every 18 months to 3 years) requires research explorations in (i) new materials, devices, and processes, (ii) new architectures and algorithms, (iii) new paradigm of logic bit representation. The focus is on fundamental new ways to compute under the umbrella of rebooting computing such as spintronics, quantum computing, adiabatic and reversible computing. Therefore, this thesis highlights explicitly Quantum computing and Adiabatic logic, two new computing paradigms that come under the umbrella of rebooting computing. Quantum computing is investigated for its promising application in high-performance computing. The first contribution of this thesis is the design of two resource-efficient designs for quantum integer division. The first design is based on non-restoring division algorithm and the second one is based on restoring division algorithm. Both the designs are compared and shown to be superior to the existing work in terms of T-count and T-depth. The proliferation of IoT devices which work on low-power also has drawn interests to the rebooting computing. Hence, the second contribution of this thesis is proving that Adiabatic Logic is a promising candidate for implementation in IoT devices. The adiabatic logic family called Symmetric Pass Gate Adiabatic Logic (SPGAL) is implemented in PRESENT-80 lightweight algorithm. Adiabatic Logic is extended to emerging transistor devices
Perspectives on Nuclear Structure and Scattering with the Ab Initio No-Core Shell Model
Nuclear structure and reaction theory are undergoing a major renaissance with
advances in many-body methods, strong interactions with greatly improved links
to Quantum Chromodynamics (QCD), the advent of high performance computing, and
improved computational algorithms. Predictive power, with well-quantified
uncertainty, is emerging from non-perturbative approaches along with the
potential for new discoveries such as predicting nuclear phenomena before they
are measured. We present an overview of some recent developments and discuss
challenges that lie ahead. Our focus is on explorations of alternative
truncation schemes in the harmonic oscillator basis, of which our
Japanese--United States collaborative work on the No-Core Monte-Carlo Shell
Model is an example. Collaborations with Professor Takaharu Otsuka and his
group have been instrumental in these developments.Comment: 8 pages, 5 figures, accepted for publication in Proceedings of
Perspectives of the Physics of Nuclear Structure, JPS Conference Proceedings,
Japan (to appear
EXPLORATIONS IN QUANTUM COMPUTING FOR FINANCIAL APPLICATIONS
Quantum computers have the potential to increase the solution speed for many computational problems. This paper is a first step into possible applications for quantum computing in the context of computational finance. The fundamental ideas of quantum computing are introduced, followed by an exposition of the algorithms of Deutsch and Grover. Improved mean and median estimation are shown as results of Grover?s generalized framework. The algorithm for mean estimation is refined to an improved Monte Carlo algorithm. Quantum random number generation is also described
Exploration of Reaction Pathways and Chemical Transformation Networks
For the investigation of chemical reaction networks, the identification of
all relevant intermediates and elementary reactions is mandatory. Many
algorithmic approaches exist that perform explorations efficiently and
automatedly. These approaches differ in their application range, the level of
completeness of the exploration, as well as the amount of heuristics and human
intervention required. Here, we describe and compare the different approaches
based on these criteria. Future directions leveraging the strengths of chemical
heuristics, human interaction, and physical rigor are discussed.Comment: 48 pages, 4 figure
Topological string entanglement
We investigate how topological entanglement of Chern-Simons theory is
captured in a string theoretic realization. Our explorations are motivated by a
desire to understand how quantum entanglement of low energy open string degrees
of freedom is encoded in string theory (beyond the oft discussed classical
gravity limit). Concretely, we realize the Chern-Simons theory as the
worldvolume dynamics of topological D-branes in the topological A-model string
theory on a Calabi-Yau target. Via the open/closed topological string duality
one can map this theory onto a pure closed topological A-model string on a
different target space, one which is related to the original Calabi-Yau
geometry by a geometric/conifold transition. We demonstrate how to uplift the
replica construction of Chern-Simons theory directly onto the closed string and
show that it provides a meaningful definition of reduced density matrices in
topological string theory. Furthermore, we argue that the replica construction
commutes with the geometric transition, thereby providing an explicit closed
string dual for computing reduced states, and Renyi and von Neumann entropies
thereof. While most of our analysis is carried out for Chern-Simons on S^3, the
emergent picture is rather general. Specifically, we argue that quantum
entanglement on the open string side is mapped onto quantum entanglement on the
closed string side and briefly comment on the implications of our result for
physical holographic theories where entanglement has been argued to be crucial
ingredient for the emergence of classical geometry.Comment: 48 pages + appendices, many tikz fgures. v2: added clarification
Qutrit Circuits and Algebraic Relations: A Pathway to Efficient Spin-1 Hamiltonian Simulation
Quantum information processing has witnessed significant advancements through
the application of qubit-based techniques within universal gate sets. Recently,
exploration beyond the qubit paradigm to -dimensional quantum units or
qudits has opened new avenues for improving computational efficiency. This
paper delves into the qudit-based approach, particularly addressing the
challenges presented in the high-fidelity implementation of qudit-based
circuits due to increased complexity. As an innovative approach towards
enhancing qudit circuit fidelity, we explore algebraic relations, such as the
Yang-Baxter-like turnover equation, that may enable circuit compression and
optimization. The paper introduces the turnover relation for the three-qutrit
time propagator and its potential use in reducing circuit depth. We further
investigate whether this relation can be generalized for higher-dimensional
quantum circuits, including a focused study on the one-dimensional spin-1
Heisenberg model. Our work outlines both rigorous and numerically efficient
approaches to potentially achieve this generalization, providing a foundation
for further explorations in the field of qudit-based quantum computing
Constant-Overhead Fault-Tolerant Quantum Computation with Reconfigurable Atom Arrays
Quantum low-density parity-check (qLDPC) codes can achieve high encoding
rates and good code distance scaling, providing a promising route to
low-overhead fault-tolerant quantum computing. However, the long-range
connectivity required to implement such codes makes their physical realization
challenging. Here, we propose a hardware-efficient scheme to perform
fault-tolerant quantum computation with high-rate qLDPC codes on reconfigurable
atom arrays, directly compatible with recently demonstrated experimental
capabilities. Our approach utilizes the product structure inherent in many
qLDPC codes to implement the non-local syndrome extraction circuit via atom
rearrangement, resulting in effectively constant overhead in practically
relevant regimes. We prove the fault tolerance of these protocols, perform
circuit-level simulations of memory and logical operations with these codes,
and find that our qLDPC-based architecture starts to outperform the surface
code with as few as several hundred physical qubits at a realistic physical
error rate of . We further find that less than 3000 physical qubits
are sufficient to obtain over an order of magnitude qubit savings compared to
the surface code, and quantum algorithms involving thousands of logical qubits
can be performed using less than physical qubits. Our work paves the way
for explorations of low-overhead quantum computing with qLDPC codes at a
practical scale, based on current experimental technologies
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