检索结果-内蒙古大学图书馆

Optimal adaptive testing for epidemic control: Combining molecular and serology tests

学校读者我要写书评

暂无评论

arXiv 2021年

作者： Acemoglu, D. Fallah, A. Giometto, A. Huttenlocher, D. Ozdaglar, A. Parise, Francesca Pattathil, S. United States Department of Electrical Engineering and Computer Science MIT United States School of Civil and Environmental Engineering Cornell University United States Department of Electrical and Computer Engineering Cornell University United States

The COVID-19 crisis highlighted the importance of non-medical interventions, such as testing and isolation of infected individuals, in the control of epidemics. Here, we show how to minimize testing needs while maintaining the number of infected individuals below a desired threshold. We find that the optimal policy is adaptive, with testing rates that depend on the epidemic state. Additionally, we show that such epidemic state is difficult to infer with molecular tests alone, which are highly sensitive but have a short detectability window. Instead, we propose the use of baseline serology testing, which is less sensitive but detects past infections, for the purpose of state estimation. Validation of such combined testing approach with a stochastic model of epidemics shows significant cost savings compared to non-adaptive testing strategies that are the current standard for COVID-19. Copyright © 2021, The Authors. All rights reserved.

关键词： Stochastic systems

High-Efficiency, Low-Loss Floquet-Mode Traveling-Wave Parametric Amplifier

学校读者我要写书评

暂无评论

arXiv 2025年

作者： Wang, Jennifer Peng, Kaidong Knecht, Jeffrey M. Cunningham, Gregory D. Lombo, Andres E. Yen, Alec Zaidenberg, Daniela A. Gingras, Michael Niedzielski, Bethany M. Stickler, Hannah Sliwa, Katrina Serniak, Kyle Schwartz, Mollie E. Oliver, William D. O’Brien, Kevin P. Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology CambridgeMA02139 United States Research Laboratory of Electronics Massachusetts Institute of Technology CambridgeMA02139 United States MIT Lincoln Laboratory LexingtonMA02421 United States Department of Physics Massachusetts Institute of Technology CambridgeMA02139 United States

Advancing fault-tolerant quantum computing and fundamental science necessitates quantum-limited amplifiers with near-ideal quantum efficiency and multiplexing capability. However, existing solutions typically achieve one at the expense of the other. In this work, we experimentally demonstrate the first Floquet-mode traveling-wave parametric amplifier (Floquet TWPA), which achieves nearly quantum-limited noise performance, minimal dissipation, and broadband operation, breaking the presumption that broadband amplifiers introduce higher noise. We achieve a system measurement efficiency of 65.1 ± 5.8% when measuring a superconducting qubit, which to our knowledge is the highest-reported in a superconducting qubit readout experiment utilizing phase-preserving amplifiers. Our device exhibits > 20-dB amplification over a 3-GHz instantaneous bandwidth, Copyright © 2025, The Authors. All rights reserved.

关键词： Qubits

Optical properties of dispersive time-dependent materials

学校读者我要写书评

暂无评论

arXiv 2022年

作者： Sloan, Jamison Rivera, Nicholas Joannopoulos, John D. Soljačić, Marin Department of Electrical Engineering and Computer Science MIT CambridgeMA02139 United States Research Laboratory of Electronics MIT CambridgeMA02139 United States Department of Physics MIT CambridgeMA02139 United States Department of Physics Harvard University CambridgeMA02138 United States

Time-varying optical materials have attracted recent interest for their potential to enable frequency conversion, nonreciprocal physics, photonic time-crystals, and more. However, the description of time-varying materials has been primarily limited to regimes where material resonances (i.e., dispersion) can be neglected. In this work, we describe how the optics of these dispersive time-varying materials emerges from microscopic quantum mechanical models of time-driven systems. Our results are based on a framework for describing the optics of dispersive time-varying materials through quantum mechanical linear response theory. Importantly, we clarify how response functions for time-varying materials are connected to energy transfer. We provide three examples of our framework applied to systems which can be used to model a wide variety of experiments: few level models that can describe atoms, spins, or superconducting qubits, oscillator models which can describe the strong response of polar insulators, and strongly driven atom models which can describe the highly nonperturbative optical response of materials undergoing high harmonic generation. We anticipate that our results will be broadly applicable to electromagnetic phenomena in strongly time-varying systems. © 2022, CC BY.

关键词： Energy transfer

Qubit Lattice Algorithms based on the Schrodinger-Dirac representation of Maxwell Equations and their Extensions

学校读者我要写书评

暂无评论

arXiv 2023年

作者： Vahala, George Soe, Min Koukoutsis, Efstratios Hizanidis, Kyriakos Vahala, Linda Ram, Abhay K. Department of Physics William & Mary WilliamsburgVA23185 United States Department of Mathematics and Physical Sciences Rogers State University ClaremoreOK74017 United States School of Electrical and Computer Engineering National Technical University of Athens Zographou15780 Greece Department of Electrical & Computer Engineering Old Dominion University NorfolkVA23529 United States Plasma Science and Fusion Center MIT CambridgeMA02139 United States

It is well known that Maxwell equations can be expressed in a unitary Schrodinger-Dirac representation for homogeneous media. However, difficulties arise when considering inhomogeneous media. A Dyson map points to a unitary field qubit basis, but the standard qubit lattice algorithm of interleaved unitary collision-stream operators must be augmented by some sparse non-unitary potential operators that recover the derivatives on the refractive indices. The effect of the steepness of these derivatives on two dimensional scattering is examined with simulations showing quite complex wavefronts emitted due to transmissions/reflections within the dielectric objects. Maxwell equations are extended to handle dissipation using Kraus operators. Then, our theoretical algorithms are extended to these open quantum systems. A quantum circuit diagram is presented as well as estimates on the required number of quantum gates for implementation on a quantum computer. © 2023, CC BY.

关键词： Maxwell equations

Qubit Lattice Algorithm Simulations of Maxwell's Equations for Scattering from Anisotropic Dielectric Objects

学校读者我要写书评

暂无评论

arXiv 2023年

作者： Vahala, George Soe, Min Vahala, Linda Ram, Abhay K. Koukoutsis, Efstratios Hizanidis, Kyriakos Department of Physics William & Mary WilliamsburgVA23185 United States Department of Mathematics and Physical Sciences Rogers State University ClaremoreOK74017 United States Department of Electrical & Computer Engineering Old Dominion University NorfolkVA23529 United States Plasma Science and Fusion Center MIT CambridgeMA02139 United States School of Electrical and Computer Engineering National Technical University of Athens Zographou15780 Greece

A Dyson map explicitly determines the appropriate basis of electromagnetic fields which yields a unitary representation of the Maxwell equations in an inhomogeneous medium. A qubit lattice algorithm (QLA) is then developed perturbatively to solve this representation of Maxwell equations. QLA consists of an interleaved unitary sequence of collision operators (that entangle on lattice-site qubits) and streaming operators (that move this entanglement throughout the lattice). External potential operators are introduced to handle gradients in the refractive indices, and these operators are typically non-unitary, but sparse matrices. By also interleaving the external potential operators with the unitary collide-stream operators one achieves a QLA which conserves energy to high accuracy. Some two dimensional simulations results are presented for the scattering of a one-dimensional (1D) pulse off a localized anisotropic dielectric object. © 2023, CC BY.

关键词： Maxwell equations

Interferometric Purcell Suppression of Spontaneous Emission in a Superconducting Qubit

学校读者我要写书评

暂无评论

arXiv 2024年

作者： Yen, Alec Ye, Yufeng Peng, Kaidong Wang, Jennifer Cunningham, Gregory Gingras, Michael Niedzielski, Bethany M. Stickler, Hannah Serniak, Kyle Schwartz, Mollie E. O'Brien, Kevin P. Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology CambridgeMA02139 United States Research Laboratory of Electronics Massachusetts Institute of Technology CambridgeMA02139 United States Harvard John A. Paulson School of Engineering and Applied Sciences Harvard University CambridgeMA02138 United States MIT Lincoln Laboratory LexingtonMA02421 United States

In superconducting qubits, suppression of spontaneous emission is essential to achieve fast dispersive measurement and reset without sacrificing qubit lifetime. We show that resonator-mediated decay of the qubit mode to the feedline can be suppressed using destructive interference, where the readout resonator is coupled to the feedline at two points. This "interferometric Purcell filter" does not require dedicated filter components or impedance mismatch in the feedline, making it suitable for applications such as all-pass readout. We design and fabricate a device with the proposed scheme and demonstrate suppression of resonator-mediated decay that exceeds 2 orders of magnitude over a bandwidth of 400MHz. Copyright © 2024, The Authors. All rights reserved.

关键词： Spontaneous emission

Directional Emission of a Readout Resonator for Qubit Measurement

学校读者我要写书评

暂无评论

arXiv 2024年

作者： Yen, Alec Ye, Yufeng Peng, Kaidong Wang, Jennifer Cunningham, Gregory Gingras, Michael Niedzielski, Bethany M. Stickler, Hannah Serniak, Kyle Schwartz, Mollie E. O’Brien, Kevin P. Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology CambridgeMA02139 United States Research Laboratory of Electronics Massachusetts Institute of Technology CambridgeMA02139 United States Harvard John A. Paulson School of Engineering and Applied Sciences Harvard University CambridgeMA02138 United States MIT Lincoln Laboratory LexingtonMA02421 United States

We propose and demonstrate transmission-based dispersive readout of a superconducting qubit using an all-pass resonator, which preferentially emits readout photons toward the output. This is in contrast to typical readout schemes, which intentionally mismatch the feedline at one end so that the readout signal preferentially decays toward the output. We show that this intentional mismatch creates scaling challenges, including larger spread of effective resonator linewidths due to non-ideal impedance environments and added infrastructure for impedance matching. A future architecture using multiplexed all-pass readout resonators would avoid the need for intentional mismatch and potentially improve the scaling prospects of quantum computers. As a proof-of-concept demonstration of "all-pass readout," we design and fabricate an all-pass readout resonator that demonstrates insertion loss below 1.17 dB at the readout frequency and a maximum insertion loss of 1.53 dB across its full bandwidth for the lowest three states of a transmon qubit. We demonstrate qubit readout with an average single-shot fidelity of 98.1% in 600 ns;to assess the effect of larger dispersive shift, we implement a shelving protocol and achieve a fidelity of 99.0% in 300 ns. Copyright © 2024, The Authors. All rights reserved.

关键词： Qubits

Evolution of 1/f Flux Noise in Superconducting Qubits with Weak Magnetic Fields

学校读者我要写书评

暂无评论

Physical Review Letters 2023年第22期130卷 220602-220602页

作者： David A. Rower Lamia Ateshian Lauren H. Li Max Hays Dolev Bluvstein Leon Ding Bharath Kannan Aziza Almanakly Jochen Braumüller David K. Kim Alexander Melville Bethany M. Niedzielski Mollie E. Schwartz Jonilyn L. Yoder Terry P. Orlando Joel I-Jan Wang Simon Gustavsson Jeffrey A. Grover Kyle Serniak Riccardo Comin William D. Oliver Department of Physics Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA Research Laboratory of Electronics Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA Department of Physics Harvard University Cambridge Massachusetts 02139 USA MIT Lincoln Laboratory Lexington Massachusetts 02421 USA

The microscopic description of 1/f magnetic flux noise in superconducting circuits has remained an open question for several decades despite extensive experimental and theoretical investigation. Recent progress in superconducting devices for quantum information has highlighted the need to mitigate sources of qubit decoherence, driving a renewed interest in understanding the underlying noise mechanism(s). Though a consensus has emerged attributing flux noise to surface spins, their identity and interaction mechanisms remain unclear, prompting further study. Here, we apply weak in-plane magnetic fields to a capacitively shunted flux qubit (where the Zeeman splitting of surface spins lies below the device temperature) and study the flux-noise-limited qubit dephasing, revealing previously unexplored trends that may shed light on the dynamics behind the emergent 1/f noise. Notably, we observe an enhancement (suppression) of the spin-echo (Ramsey) pure-dephasing time in fields up to B=100 G. With direct noise spectroscopy, we further observe a transition from a 1/f to approximately Lorentzian frequency dependence below 10 Hz and a reduction of the noise above 1 MHz with increasing magnetic field. We suggest that these trends are qualitatively consistent with an increase of spin cluster sizes with magnetic field. These results should help to inform a complete microscopic theory of 1/f flux noise in superconducting circuits.

关键词： Fluctuations & noise Open quantum systems & decoherence SQUID Superconducting qubits

Panoramic mapping of phonon transport from ultrafast electron diffraction and machine learning

学校读者我要写书评

暂无评论

arXiv 2022年

作者： Chen, Zhantao Shen, Xiaozhe Andrejevic, Nina Liu, Tongtong Luo, Duan Nguyen, Thanh Drucker, Nathan C. Kozina, Michael E. Song, Qichen Hua, Chengyun Chen, Gang Wang, Xijie Kong, Jing Li, Mingda Quantum Measurement Group MIT CambridgeMA02139 United States Department Of Mechanical Engineering MIT CambridgeMA02139 United States SLAC National Accelerator Laboratory Menlo ParkCA94205 United States Department Of Materials Science And Engineering MIT CambridgeMA02139 United States Department Of Physics MIT CambridgeMA02139 United States Department Of Nuclear Science And Engineering MIT CambridgeMA02139 United States John A. Paulson School Of Engineering And Applied Science Harvard University CambridgeMA02138 United States Materials Science And Technology Division Oak Ridge National Laboratory Oak RidgeTN37831 United States Department Of Electrical Engineering And Computer Science MIT CambridgeMA02139 United States

One central challenge in understanding phonon thermal transport is a lack of experimental tools to investigate mode-based transport information. Although recent advances in computation lead to mode-based information, it is hindered by unknown defects in bulk region and at interfaces. Here we present a framework that can reveal microscopic phonon transport information in heterostructures, integrating state-of-the-art ultrafast electron diffraction (UED) with advanced scientific machine learning. Taking advantage of the dual temporal and reciprocal-space resolution in UED, we are able to reliably recover the frequency-dependent interfacial transmittance with possible extension to frequency-dependent relaxation times of the heterostructure. This enables a direct reconstruction of real-space, real-time, frequency-resolved phonon dynamics across an interface. Our work provides a new pathway to experimentally probe phonon transport mechanisms with unprecedented details. Copyright © 2022, The Authors. All rights reserved.

关键词： Phonons