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Search Publications by

Neil M. Zimmerman (Fed)

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Displaying 1 - 25 of 80

National Institute of Standards and Technology Environmental Scan 2020

February 9, 2021
Heather Evans, Kristen K. Greene, William M. Healy, Elizabeth Hoffman, Kate Rimmer, Anna V. Sberegaeva, Neil M. Zimmerman
The 2020 National Institute of Standards and Technology Environmental Scan provides an analysis of key external factors that could impact NIST and the fulfillment of its mission in coming years. The analyses were conducted through four separate lenses

Reduction of charge offset drift using plasma oxidized aluminum in SETs

October 26, 2020
Yanxue Hong, Ryan Stein, Michael Stewart, Neil M. Zimmerman, Joshua M. Pomeroy
Aluminum oxide (AlOx)-based single-electron transistors (SETs) fabricated in ultra-high vacuum (UHV) chambers using in situ plasma oxidation show excellent stabilities over more than a week, enabling applications as tunnel barriers, capacitor dielectrics

The Next Generation of Current Measurement for Ionization Chambers

September 1, 2020
Ryan P. Fitzgerald, Denis E. Bergeron, Dean G. Jarrett, Neil M. Zimmerman, Carine Michotte, Hansjoerg Scherer, Stephen Giblin, Steven Judge
Re-entrant ionization chambers (ICs) are essential to radionuclide metrology and nuclear medicine for maintaining standards and measuring half-lives. Metrology-quality systems must be precise and stable to 0.1% over many years, and linear from 10^(-14) A

Ohms Law Low-current Calibration System for Ionization Chambers

August 24, 2020
Dean G. Jarrett, Shamith U. Payagala, Ryan P. Fitzgerald, Denis E. Bergeron, Jeffrey T. Cessna, Charles J. Waduwarage Perera, Neil M. Zimmerman
A system for the calibration of electrometers that measure currents from ionization chambers is described. The calibration system uses a 1 GΩ standard resistor in series with a stable voltage source to generate calibration currents from 1 pA to 20 nA

Long-term drift of Si-MOS quantum dots with intentional donor implants

May 21, 2019
m rudolph, B Sarabi, Roy E. Murray, M Carroll, Neil M. Zimmerman
Charge noise can be detrimental to the operation of quantum dot (QD) based semiconductor qubits. We study the low-frequency charge noise by charge o set drift measurements for Si-MOS devices with intentionally implanted donors near the QDs. We show that

Machine Learning techniques for state recognition and auto-tuning in quantum dots

January 21, 2019
Sandesh Kalantre, Justyna Zwolak, Stephen Ragole, Xingyao Wu, Neil M. Zimmerman, Michael Stewart, Jacob Taylor
Recent progress in building large-scale quantum devices for exploring quantum computing and simulation paradigms has relied upon effective tools for achieving and maintaining good experimental parameters, i.e. tuning up devices. In many cases, including in

Spin decoherence in a two-qubit CPHASE gate: the critical role of tunneling noise

November 27, 2018
Peihao Huang, Neil M. Zimmerman, Garnett W. Bryant
The rapid progress in the manipulation and detection of semiconductor spin qubits enables the experimental demonstration of a high fidelity two-qubit logic gate, which is necessary for universal quantum computing. Here, we study the decoherence of two

Effect of device design on charge offset drift in Si/SiO2 single electron devices

October 9, 2018
Binhui Hu, Erick Ochoa, Daniel Sanchez, Justin K. Perron, Neil M. Zimmerman, Michael Stewart
We have measured the low-frequency time instability known as charge offset drift of Si/SiO2 single electron devices (SEDs) with and without an overall poly-Si top gate. We find that SEDs with a poly-Si top gate have significantly less charge offset drift

Towards superconductivity in p-type delta-doped Si/Al/Si heterostructures

July 30, 2018
Aruna N. Ramanayaka, Hyun Soo Kim, Joseph A. Hagmann, Roy E. Murray, Ke Tang, Neil M. Zimmerman, Curt A. Richter, Joshua M. Pomeroy, Frederick Meisenkothen, Huairuo Zhang, Albert Davydov, Leonid A. Bendersky
In pursuit of superconductivity in p-type silicon (Si), we are using a single atomic layer of aluminum (Al) sandwiched between a Si substrate and a thin Si epi-layer. The delta layer was fabricated starting from an ultra high vacuum (UHV) flash anneal of

AC Signal Characterization for Optimization of a CMOS Single Electron Pump

January 8, 2018
Roy E. Murray, Justin K. Perron, Michael D. Stewart, Neil M. Zimmerman
Pumping single electrons at a set rate is being widely pursued as an electrical current standard. Much work has been done on pumping using a single AC signal, but using multiple coordinated AC signals may help lower error rates. Whether pumping with one or

Valley blockade in a silicon double quantum dot

November 13, 2017
Justin K. Perron, Michael Gullans, Jacob Taylor, Michael Stewart, Neil M. Zimmerman
Electrical transport in double quantum dots (DQD) is useful for illuminating many interesting aspects of the carrier states in quantum dots. Here we show data comparing bias triangles (i.e., regions of allowed current in DQDs) at positive and negative bias

Valley Phase and Voltage Control of Coherent Manipulation in Si Quantum Dots

June 28, 2017
Neil M. Zimmerman, Peihao Huang, Dimitrie Culcer
With any roughness at the interface of an indirect-bandgap semiconducting dot, the phase of the valley-orbit coupling can take on a random value. This random value, in double quantum dots, causes a large change in the exchange splitting. We demonstrate a

An electrically driven spin qubit based on valley mixing

February 2, 2017
wister huang, Neil M. Zimmerman, Andrew S. Dzurak, Dimitrie Culcer
The electrical control of single spin qubits based on semiconductor quantum dots is of great interest for scalable quantum computing since electric elds are much easier to produce and spatially focus than magnetic elds. Here we outline the mechanism for a

Stability of Single Electron Devices: Charge Offset Drift

June 29, 2016
Michael D. Stewart, Neil M. Zimmerman
Abstract: Single electron devices (SEDs) afford the opportunity to isolate and manipulate individual electrons. This ability imbues SEDs with potential applications in a wide array of areas from metrology (current and capacitance) to quantum information

A New Regime of Pauli-Spin Blockade

April 7, 2016
Justin K. Perron, Michael D. Stewart, Neil M. Zimmerman
Pauli-spin blockade is a phenomenon that allows for a type of spin to charge conversion often used to probe fundamental physics such as spin relaxation and singlet-triplet coupling. In this paper we theoretically explore Pauli-spin blockade as a function

Formation of Strain Induced Quantum Dots in Gated Semiconductor Nanostructures

August 5, 2015
Ted C. Thorbeck, Neil M. Zimmerman
Elastic strain changes the energies of the conduction and valence bands in a semiconductor, which will affect transport through a semiconductor nanostructure. We show that the typical strains in a semiconductor nanostructure arising from metal gates or

The Redefinition of the SI: Impact on Calibration Services at NIST

June 1, 2015
Neil M. Zimmerman, Jon R. Pratt, Michael R. Moldover, David B. Newell, Gregory F. Strouse
As most readers are probably at least vaguely aware, it is likely that the SI system of units will be redefied in 2018. This redefinition would fundamentally change the logical structure of the SI, with one result being a substantial change in how mass is

Charge Offset Stability in Si Single Electron Devices with Al Gates

September 19, 2014
Neil M. Zimmerman, Henry Yang, Nai Shyan Lai, Wee Han Lim, Andrew S. Dzurak
We report on the charge offset drift (time stability) in Si quantum dots defined with Al gates. The size of the charge offset drift (0.1 e) is intermediate between that of Al/AlO_x/Al tunnel junctions (greater than 1 e) and Si quantum dots defined with Si

Dephasing of Si singlet-triplet qubits due to charge and spin defects

June 14, 2013
Dimitrie Culcer, Neil M. Zimmerman
We study the effect of charge and spin noise on singlet-triplet qubits in Si quantum dots. We set up a theoretical framework aimed at enabling experiment to efficiently identify the most deleterious defects, and complement it with the knowledge of defects