Quantum Brain

Papers

Live trends in quantum computing research, updated daily from arXiv.

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13,351 papers in 12 months (+7% vs prior quarter)

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4,120 papers found

Optimizing the Spin Reversal Transform on the D-Wave 2000Q

Elijah Pelofske, Georg Hahn, H. Djidjev·Jun 26, 2019

Commercial quantum annealers from D-Wave Systems make it possible to obtain approximate solutions of high quality for certain NP-hard problems in nearly constant time. Before solving a problem on D-Wave, several pre-processing methods can be applied,...

MathematicsComputer SciencePhysics

Quasiexact Kondo Dynamics of Fermionic Alkaline-Earth-Like Atoms at Finite Temperatures.

S. Goto, I. Danshita·Jun 21, 2019

A recent experiment has observed the antiferromagnetic interaction between the ground state ^{1}S_{0} and the metastable state ^{3}P_{0} of ^{171}Yb atoms, which are fermionic. This observation combined with the use of state-dependent optical lattice...

PhysicsMedicine

High-fidelity single-qubit gates in a strongly driven quantum-dot hybrid qubit with1/fcharge noise

Yuan-Chi Yang, S. Coppersmith, M. Friesen·Jun 19, 2019

Semiconductor double quantum dot hybrid qubits are promising candidates for high-fidelity quantum computing. However, their performance is limited by charge noise, which is ubiquitous in solid-state devices, and phonon-induced dephasing. Here we expl...

Physics

Approaching graph problems with continuous variable quantum computing.

Michal Stkechly, N. Bashige, Przemyslaw Chojecki·Jun 17, 2019

We introduce a method for solving the Max-Cut problem using a variational algorithm and a continuous-variables quantum computing approach. The quantum circuit consists of two parts: the first one embeds a graph into a circuit using the Takagi decompo...

MathematicsPhysics

Mitigating coherent noise using Pauli conjugation

Z. Cai, Xiaosi Xu, S. Benjamin·Jun 14, 2019

Coherent noise can be much more damaging than incoherent (probabilistic) noise in the context of quantum error correction. One solution is to use twirling to turn coherent noise into incoherent Pauli channels. In this Article, we show that some of th...

PhysicsComputer Science

Synthesizing Quantum Circuits via Numerical Optimization

T. Brugière, M. Baboulin, Benoît Valiron +1 more·Jun 12, 2019

We provide a simple framework for the synthesis of quantum circuits based on a numerical optimization algorithm. This algorithm is used in the context of the trapped-ions technology. We derive theoretical lower bounds for the number of quantum gates ...

Computer SciencePhysics

Wave-function positivization via automatic differentiation

G. Torlai, J. Carrasquilla, M. Fishman +2 more·Jun 11, 2019

We introduce a procedure to systematically search for a local unitary transformation that maps a wavefunction with a non-trivial sign structure into a positive-real form. The transformation is parametrized as a quantum circuit compiled into a set of ...

PhysicsComputer Science

Phase Gadget Synthesis for Shallow Circuits

Alexander Cowtan, Silas Dilkes, Ross Duncan +2 more·Jun 4, 2019

We give an overview of the circuit optimisation methods used by tket, a compiler system for quantum software developed by Cambridge Quantum Computing Ltd. We focus on a novel technique based around phase gadgets, a family of multi-qubit quantum opera...

Computer SciencePhysics

Noise reduction using past causal cones in variational quantum algorithms

Omar Shehab, Isaac H. Kim, N. Nguyen +5 more·Jun 2, 2019

We introduce an approach to improve the accuracy and reduce the sample complexity of near term quantum-classical algorithms. We construct a simpler initial parameterized quantum state, or ansatz, based on the past causal cone of each observable, gene...

Computer SciencePhysicsMathematics

Superconducting Qubits: Current State of Play

M. Kjaergaard, M. Schwartz, Jochen Braumuller +4 more·May 31, 2019

Superconducting qubits are leading candidates in the race to build a quantum computer capable of realizing computations beyond the reach of modern supercomputers. The superconducting qubit modality has been used to demonstrate prototype algorithms in...

PhysicsComputer Science

Dual-species, multi-qubit logic primitives for Ca+/Sr+ trapped-ion crystals

C. Bruzewicz, R. McConnell, J. Stuart +2 more·May 30, 2019

We demonstrate key multi-qubit quantum-logic primitives in a dual-species trapped-ion system based on $${}^{40}$$40Ca$${}^{+}$$+ and $${}^{88}$$88Sr$${}^{+}$$+ ions, using two optical qubits with quantum-logic-control frequencies in the red to near-i...

PhysicsMathematics

Experimental Hamiltonian Learning of an 11-Qubit Solid-State Quantum Spin Register*

P. Hou, L. He, F. Wang +7 more·May 29, 2019

Learning Hamiltonian of a quantum system is indispensable for prediction of the system dynamics and realization of high fidelity quantum gates. However, it is a significant challenge to efficiently characterize the Hamiltonian when its Hilbert space ...

PhysicsMathematics

Full-Stack, Real-System Quantum Computer Studies: Architectural Comparisons and Design Insights

Prakash Murali, N. Linke, M. Martonosi +3 more·May 27, 2019

In recent years, Quantum Computing (QC) has progressed to the point where small working prototypes are available for use. Termed Noisy Intermediate-Scale Quantum (NISQ) computers, these prototypes are too small for large benchmarks or even for Quantu...

PhysicsComputer Science

Expressibility and Entangling Capability of Parameterized Quantum Circuits for Hybrid Quantum‐Classical Algorithms

Sukin Sim, Peter D. Johnson, Alán Aspuru-Guzik·May 26, 2019

Parameterized quantum circuits (PQCs) play an essential role in the performance of many variational quantum algorithms. One challenge in implementing such algorithms is choosing an effective circuit that well represents the solution space while maint...

Computer SciencePhysics

Error correction schemes for fully correlated quantum channels protecting both quantum and classical information

Chi-Kwong Li, Seth Lyles, Y. Poon·May 24, 2019

We study efficient quantum error correction schemes for the fully correlated channel on an n-qubit system with error operators that assume the form σx⊗n\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \use...

PhysicsComputer Science

Error-mitigated quantum gates exceeding physical fidelities in a trapped-ion system

Shuaining Zhang, Yao Lu, Kuan Zhang +4 more·May 24, 2019

Various quantum applications can be reduced to estimating expectation values, which are inevitably deviated by operational and environmental errors. Although errors can be tackled by quantum error correction, the overheads are far from being affordab...

MedicineComputer ScienceBiologyPhysics

Power-optimal, stabilized entangling gate between trapped-ion qubits

R. Blümel, Nikodem Grzesiak, N. Pisenti +2 more·May 22, 2019

To achieve scalable quantum computing, improving entangling-gate fidelity and its implementation efficiency are of utmost importance. We present here a linear method to construct provably power-optimal entangling gates on an arbitrary pair of qubits ...

Computer SciencePhysics

Efficient arbitrary simultaneously entangling gates on a trapped-ion quantum computer

Nikodem Grzesiak, R. Blümel, K. Wright +8 more·May 22, 2019

Efficiently entangling pairs of qubits is essential to fully harness the power of quantum computing. Here, we devise an exact protocol that simultaneously entangles arbitrary pairs of qubits on a trapped-ion quantum computer. The protocol requires cl...

PhysicsComputer ScienceMedicine

Short-depth circuits for efficient expectation-value estimation

A. Roggero, A. Baroni·May 21, 2019

The evaluation of expectation values $Tr\left[\rho O\right]$ for some pure state $\rho$ and Hermitian operator $O$ is of central importance in a variety of quantum algorithms. Near optimal techniques developed in the past require a number of measurem...

Physics

Protocol for a resonantly driven three-qubit Toffoli gate with silicon spin qubits

M. Gullans, J. Petta·May 16, 2019

The three-qubit Toffoli gate plays an important role in quantum error correction and complex quantum algorithms such as Shor's factoring algorithm, motivating the search for efficient implementations of this gate. Here we introduce a Toffoli gate sui...

Physics
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