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Qubit-Efficient Quantum Chemistry with the ADAPT Variational Quantum Eigensolver and Double Unitary Downfolding
Here, in this work, we combine the recently developed double unitary coupled cluster (DUCC) theory with the adaptive, problem-tailored variational quantum eigensolver (ADAPT-VQE) to explore the accuracy of unitary downfolded Hamiltonians for quantum simulation of chemistry. We benchmark the ability of DUCC effective Hamiltonians to recover dynamical correlation energy outside of an active space. We consider the effects of strong correlation, commutator truncation, higher-body terms, and approximate external amplitudes on the accuracy of these effective Hamiltonians. When combining these DUCC Hamiltonians with ADAPT-VQE, we observe similar convergence of the ground state as compared with bare active space Hamiltonians, demonstrating that DUCC Hamiltonians provide increased accuracy without increasing the load on the quantum processor.
Strategy for Addressing the Low Quantum Efficiency of Nanowire Photodetectors
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Direct In Situ Measurement of Quantum Efficiencies of Charge Separation and Proton Reduction at TiO 2 -Protected GaP Photocathodes
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14.8% Quantum Efficient Gallium Phosphide Photocatalyst for Hydrogen Evolution
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Highly-efficient quantum Fourier transformations for certain non-Abelian groups
Quantum Fourier transformations are an essential component of many quantum algorithms, from prime factoring to quantum simulation. While the standard Abelian QFrT is well studied, important variants corresponding to non-Abelian groups of interest have seen less development. In particular, fast non-Abelian Fourier transformations are important components for both quantum simulations of field theories as well as approaches to the non-Abelian hidden subgroup problem. In this work, we present fast quantum Fourier transformations for a number of non-Abelian groups of interest for high energy physics, B T , B O , 6 Δ ( 27 ) , Δ ( 54 ) , and Σ ( 36 × 3 ) . For each group, we derive explicit quantum circuits and estimate resource scaling for fault-tolerant implementations. Our work shows that the development of a fast Fourier transformation can substantively reduce simulation costs by an up to three orders of magnitude for the finite groups that we have investigated.
Efficient quantum computation of molecular forces and other energy gradients
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Even More Efficient Quantum Computations of Chemistry Through Tensor Hypercontraction
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Efficient Quantum Circuit Decompositions via Intermediate Qudits
Many quantum algorithms make use of ancilla, additional qubits used to store temporary information during computation, to reduce the total execution time. Quantum computers will be resource-constrained for years to come so reducing ancilla requirements is crucial. In this work, we give a method to generate ancilia out of idle qubits by placing some in higher-value states, called qudits. Here, we show how to take a circuit with many O(n) ancilla and design an ancilla-free circuit with the same asymptotic depth. Using this, we give a circuit construction for an in-place adder and a constant adder both with O(log n) depth using temporary qudits and no ancilla.
Efficient Quantum Gate Discovery with Optimal Control
Optimal control theory provides a framework for numerical discovery of device controls that implement quantum logic gates, but common objective functions used for optimization often assign arbitrarily high costs to otherwise useful controls. We propose a framework for designing objective functions that permit novel gate designs such as echo pulses or locally-equivalent gates. We use numerical simulations to demonstrate the efficacy of the new objective functions by designing microwave-only pulses that act as entangling gates for superconducting transmon architectures. We observe that the proposed objective functions lead to higher fidelity controls in fewer optimization iterations than obtainable by traditional objective functions.
Record quantum efficiency from superlattice photocathode for spin polarized electron beam production.
Abstract not provided.
Partial Charge Collection and Quantum Efficiency of a Back-Illuminated Skipper-CCD
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An efficient quantum algorithm for building effective Hamiltonians on fault-tolerant hardware
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Skipper-CCD Quantum Efficiency Analysis
Scientific skipper-CCDs with single-electron resolution present dozens of possibilities for detecting dark matter candidates. Fermilab's Cosmic Physics Center contributes to the DarkNESS mission, which aims to place a skipper multi-chip module in a 6U CubeSat designed for low earth orbit. The DarkNESS nanosat will have the capability to search for 1-10keV band X-rays that may originate from DM decays. One of the challenges of detection in space is the large amount of cosmic radiation contributing to sensor noise. To mitigate this, an aluminum shield is proposed to be placed on the sensor. This project aims to test and characterize the energy resolution with a shield of various thicknesses (0-100nm) using a single CCD and an iron-55 x-ray source. ROOT analysis was used to parse data from several runs into sections based on shield thickness, create strategic data cuts, and characterize Fano plus signal shot noise in the sensor.
Improved forward voltage and external quantum efficiency scaling in multi-active region III-nitride LEDs
Ultra-low voltage drop tunnel junctions (TJs) were utilized to enable multi-active region blue light emitting diodes (LEDs) with up to three active regions in a single device. The multi-active region blue LEDs were grown monolithically by metal-organic chemical vapor deposition (MOCVD) without growth interruption. This is the first demonstration of a MOCVD grown triple-junction LED. Optimized TJ design enabled near-ideal voltage and EQE scaling close to the number of junctions. Furthermore, this work demonstrates that with proper TJ design, improvements in wall-plug efficiency at high output power operation are possible by cascading multiple III-nitride based LEDs.