A5047005219- Quantum Computing Algorithms and Architecture
- Quantum Information and Cryptography
- Quantum Mechanics and Applications
- Complexity and Algorithms in Graphs
- Machine Learning and Algorithms
- Computability, Logic, AI Algorithms
- Quantum-Dot Cellular Automata
- Quantum and electron transport phenomena
- Cloud Computing and Resource Management
- Sparse and Compressive Sensing Techniques
- Integrated Circuits and Semiconductor Failure Analysis
- Advanced X-ray Imaging Techniques
- Parallel Computing and Optimization Techniques
- Markov Chains and Monte Carlo Methods
- Blind Source Separation Techniques
- Optimization and Search Problems
- Advanced Measurement and Metrology Techniques
- Medical Imaging Techniques and Applications
- Advanced X-ray and CT Imaging
- Radiation Dose and Imaging
- Spacecraft and Cryogenic Technologies
- Logic, Reasoning, and Knowledge
- Constraint Satisfaction and Optimization
- Neural Networks and Reservoir Computing
- Semiconductor materials and devices
Middlebury College
2017-2024
Joint Center for Quantum Information and Computer Science
2015-2017
University of Maryland, College Park
2015-2017
RTX (United States)
2014-2015
Massachusetts Institute of Technology
2012-2015
Center for Theoretical Biological Physics
2012-2013
Williams College
2008-2009
The great promise of quantum computers comes with the dual challenges building them and finding their useful applications. We argue that these two should be considered together, by codesigning full-stack computer systems along applications in order to hasten development potential for scientific discovery. In this context, we identify community needs, opportunities, a sampling few use case studies, significant science over next 2–10 years. This document is written university, national...
An important step in building a quantum computer is calibrating experimentally implemented gates to produce operations that are close ideal unitaries. The calibration involves estimating the systematic errors and then using controls correct implementation. Quantum process tomography standard technique for these errors, but both time consuming, (when one only wants learn few key parameters), usually inaccurate without resources like perfect state preparation measurement, which might not be...
We describe how randomized benchmarking can be used to reconstruct the unital part of any trace-preserving quantum map, which in turn is sufficient for full characterization unitary evolution, or more generally, evolution. This approach inherits benchmarking's robustness preparation, measurement, and gate imperfections, therefore avoiding systematic errors caused by these imperfections. also extend techniques efficiently estimate average fidelity a map maps outside Clifford group. The...
Typical quantum gate tomography protocols struggle with a self-consistency problem: the operation cannot be reconstructed without knowledge of initial state and final measurement, but such obtained well-characterized gates. A recently proposed technique, known as randomized benchmarking (RBT), sidesteps this problem by designing experiments to insensitive preparation measurement imperfections. We implement proposal in superconducting qubit system, using number experimental improvements...
We investigate the sample complexity of Hamiltonian simulation: how many copies an unknown quantum state are required to simulate a encoded by density matrix that state? show procedure proposed Lloyd, Mohseni, and Rebentrost [Nat. Phys., 10(9):631--633, 2014] is optimal for this task. further extend their method case multiple input states, showing any Hermitian polynomial states provided. As applications, we derive algorithms commutator simulation orthogonality testing, give protocol...
We demonstrate an experimental implementation of robust phase estimation (RPE) to learn the a single-qubit rotation on trapped ${\mathrm{Yb}}^{+}$ ion qubit. show this can be estimated with uncertainty below $4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}\text{ }\text{ }\mathrm{rad}$ using as few 176 total samples, and our estimates exhibit Heisenberg scaling. Unlike standard protocols, RPE neither assumes perfect state preparation measurement, nor requires access ancillae....
For certain joint measurements on a pair of spatially separated particles, we ask how much entanglement is needed to carry out the measurement exactly. class orthogonal two qubits with partially entangled eigenstates, present upper and lower bounds cost. The bound based recent result by D. Berry [Phys. Rev. A 75, 032349 (2007)]. bound, production capacity measurement, implies that for almost all in consider, required perform strictly greater than average its eigenstates. On other hand, show...
We give a quantum algorithm for evaluating class of boolean formulas (such as NAND trees and 3-majority trees) on restricted set inputs. Due to the structure allowed inputs, our can evaluate depth $n$ tree using $O(n^{2+\log\omega})$ queries, where $\omega$ is independent depends only type subformulas within tree. also prove classical lower bound $n^{\Omega(\log\log n)}$ thus showing (small) super-polynomial speed-up.
We consider a variant of the phase retrieval problem, where vectors are replaced by unitary matrices, i.e., unknown signal is matrix U, and measurements consist squared inner products |tr(C†U)| <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> with matrices C that chosen observer. This problem has applications to quantum process tomography, when operation. show PhaseLift, convex programming algorithm for retrieval, can be adapted this...
We give a new upper bound on the quantum query complexity of deciding<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>s</mml:mi><mml:mi>t</mml:mi></mml:math>-connectivity certain classes planar graphs, and show is sometimes exponentially better than previous results. then Boolean formula evaluation reduces to deciding connectivity just such class graphs. Applying algorithm for<mml:math problems, we match the<mml:math...
We study a quantum algorithm that consists of simple Markov process, and we analyze its behavior on restricted versions Quantum 2-SAT. prove the solves these decision problems with high probability for n qubits, L clauses, promise gap c in time O(n^2 L^2 c^{−2} ). If Hamiltonian is additionally polynomially gapped, our efficiently produces state has overlap satisfying subspace. The process analogue Schoning’s probabilistic k-SAT.
We describe a method to upper bound the quantum query complexity of Boolean formula evaluation problems, using fundamental theorems about general adversary bound. This nonconstructive can give an on without producing algorithm. For example, we oracle problem which prove (non-constructively) be solved in $O(1)$ queries, where previous best algorithm uses polylogarithmic number queries. then explicit $O(1)$-query for this based span programs.
We study the ability of efficient quantum verifiers to decide properties exponentially large subsets given either a classical or witness. develop general framework that can be used prove QCMA machines, with only witnesses, cannot verify certain implicitly via an oracle. use this oracle separation between and QMA using in-place permutation oracle, making first progress on question since Aaronson Kuperberg in 2007 [Aaronson Kuperberg, 2007]. also particularly simple standard AM.
We present an extension to the robust phase estimation protocol, which can identify incorrect results that would otherwise lie outside expected statistical range. Robust is increasingly a method of choice for applications such as estimating effective process parameters noisy hardware, but its robustness dependent on noise satisfying certain threshold assumptions. provide consistency checks indicate when those thresholds have been violated, be difficult or impossible test directly. these...
We show that the quantum query complexity of evaluating NAND-tree instances with average choice at most $W$ is $O(W)$, where a measure difficulty winning associated two-player game. This generalizes superpolynomial speedup over classical due to Zhan et al. [Zhan al., ITCS 2012, 249-265]. further player strategy for game can win an expected $\widetilde{O}(N^{1/4}\sqrt{{\cal C}(x)})$ queries against random opponent, ${\cal C }(x)$ instance. gives improvement naive strategy, which costs...
We give a new upper bound on the quantum query complexity of deciding $st$-connectivity certain classes planar graphs, and show is sometimes exponentially better than previous results. then Boolean formula evaluation reduces to connectivity just such class graphs. Applying algorithm for problems, we match $O(\sqrt{N})$ evaluating formulas $N$ variables, quadratic speed-up over classical promise formulas, this approach can yield superpolynomial quantum/classical separations. These results...