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Coherent manipulation of electron spins is one of the central challenges of silicon-based quantum computing efforts. Electron spin resonance (ESR) lines, or Oersted lines, allow 10–60 GHz radio frequency (RF) pulses to induce an electromagnetic field that drives Rabi oscillations in a quantum dot interface. The frequency of these Rabi oscillations is directly proportional to the strength of the induced electromagnetic field. We outline a methodology for the design of a printed circuit board and an ESR line that is able to transmit an RF pulse in the 40 GHz regime and induce an oscillating magnetic field onto a qubit device. We propose and implement a novel design by coupling a second symmetrical Oersted line in the opposing direction of the first to act as an antenna for the purpose of monitoring power and magnetic field strength at the embedded device interface. [ABSTRACT FROM AUTHOR]

The need for reliable quantum light sources drives our research to study color centers (CCs) in silicon as telecommunication O-band emitters. Building from photoluminescence measurements, we compare new electroluminescence measurements. To this end, we synthesized CC-embedded p-i-n junctions in silicon, creating CC light-emitting diode devices. The two types of CCs synthesized were G-centers and W-centers, which show zero-phonon lines at approximately 1279 nm and 1218 nm, respectively. Here, we present our device design, fabrication process flow, and report on the device performance results from measurements to date. [ABSTRACT FROM AUTHOR]

P+ monolayers in Si are of great scientific and technological interest, both intrinsically as a material in the "ideal vacuum" of crystalline Si and because they are showing great promise as qubits of electron and nuclear spin. The GHz complex conductivity σ(ω) can allow one to elucidate basic physical properties and is also important for fast devices, but measuring σ(ω) in 2D materials has not been easy. We report on such measurements, including showing (i) qualitatively a lack of any resonances up to 5 GHz (indicating no energy splittings below about 0.02 meV); and (ii) the quantitatively ideal Drude behavior of this novel material up to 5 GHz, showing a lower bound on the scattering rate of about 2 × 1010 s−1. We also discuss deconvolving the confounding effect of the distributed resistance and capacitance of the monolayer. [ABSTRACT FROM AUTHOR]

The Hubbard model is an essential tool for understanding many-body physics in condensed matter systems. Artificial lattices of dopants in silicon are a promising method for the analog quantum simulation of extended Fermi-Hubbard Hamiltonians in the strong interaction regime. However, complex atom-based device fabrication requirements have meant emulating a tunable two-dimensional Fermi-Hubbard Hamiltonian in silicon has not been achieved. Here, we fabricate 3 × 3 arrays of single/few-dopant quantum dots with finite disorder and demonstrate tuning of the electron ensemble using gates and probe the many-body states using quantum transport measurements. By controlling the lattice constants, we tune the hopping amplitude and long-range interactions and observe the finite-size analogue of a transition from metallic to Mott insulating behavior. We simulate thermally activated hopping and Hubbard band formation using increased temperatures. As atomically precise fabrication continues to improve, these results enable a new class of engineered artificial lattices to simulate interactive fermionic models. Atomically precise artificial lattices of dopant-based quantum dots offer a tunable platform for simulations of interacting fermionic models. By leveraging advances in fabrication and atomic-state control, Wang et al. report quantum simulations of the 2D Fermi-Hubbard model on a 3 × 3 few-dopant quantum dot array. [ABSTRACT FROM AUTHOR]

The Hubbard model is an essential tool for understanding many-body physics in condensed matter systems. Artificial lattices of dopants in silicon are a promising method for the analog quantum simulation of extended Fermi-Hubbard Hamiltonians in the strong interaction regime. However, complex atom-based device fabrication requirements have meant emulating a tunable two-dimensional Fermi-Hubbard Hamiltonian in silicon has not been achieved. Here, we fabricate 3 × 3 arrays of single/few-dopant quantum dots with finite disorder and demonstrate tuning of the electron ensemble using gates and probe the many-body states using quantum transport measurements. By controlling the lattice constants, we tune the hopping amplitude and long-range interactions and observe the finite-size analogue of a transition from metallic to Mott insulating behavior. We simulate thermally activated hopping and Hubbard band formation using increased temperatures. As atomically precise fabrication continues to improve, these results enable a new class of engineered artificial lattices to simulate interactive fermionic models. Atomically precise artificial lattices of dopant-based quantum dots offer a tunable platform for simulations of interacting fermionic models. By leveraging advances in fabrication and atomic-state control, Wang et al. report quantum simulations of the 2D Fermi-Hubbard model on a 3 × 3 few-dopant quantum dot array. [ABSTRACT FROM AUTHOR]

Atomically precise donor-based quantum devices are a promising candidate for solid-state quantum computing and analog quantum simulations. However, critical challenges in atomically precise fabrication have meant systematic, atomic scale control of the tunneling rates and tunnel coupling has not been demonstrated. Here using a room temperature grown locking layer and precise control over the entire fabrication process, we reduce unintentional dopant movement while achieving high quality epitaxy in scanning tunnelling microscope (STM)-patterned devices. Using the Si(100)2 × 1 surface reconstruction as an atomically-precise ruler to characterize the tunnel gap in precision-patterned single electron transistors, we demonstrate the exponential scaling of the tunneling resistance on the tunnel gap as it is varied from 7 dimer rows to 16 dimer rows. We demonstrate the capability to reproducibly pattern devices with atomic precision and a donor-based fabrication process where atomic scale changes in the patterned tunnel gap result in the expected changes in the tunneling rates. Donor-based solid state quantum computing devices require atomically precise fabrication and atomic-scale control of the tunneling processes. The authors describe the reproducible fabrication of a series of single electron transistors with tunnel gaps that vary based on the surface lattice and demonstrate the exponential scaling of tunneling as a function of atomically precise changes as theoretically predicted. [ABSTRACT FROM AUTHOR]

The key building blocks for the fabrication of devices based on the deterministic placement of dopants in silicon using scanning tunneling microscopy (STM) hydrogen lithography are the formation of well-defined dopant delta-layers and the overgrowth of high quality crystalline Si. To develop these capabilities, it is of critical importance to quantify dopant movement in the subnanometer regime. To this end, we investigate Si:P delta-layer samples produced by fully exposing a Si surface to PH3 prior to Si encapsulation with dramatically different levels of dopant confinement. We examine the effect of delta layer confinement on the weak localization signal in parallel and perpendicular magnetic fields and extract the delta-layer thickness from fits to the Hikami- Larkin-Nagaoka equation. We find good agreement with secondary ion mass spectroscopy measurements and demonstrate the applicability of this method in the sub-nanometer thickness regime. Our analysis serves as detailed instruction for the determination of the conducting layer thickness of a Si:P delta-layer by means of a high-throughput, nondestructive electrical transport measurement. [ABSTRACT FROM AUTHOR]

Reducing the scale of etched nanostructures below the 10 nm range eventually will require an atomic scale understanding of the masks being used in order to maintain exquisite control over both feature size and feature density. Here, the authors demonstrate a method for tracking atomically resolved and controlled structures from initial template definition through final nanostructure metrology, opening up a pathway for top-down atomic control over nanofabrication. First, hydrogen depassivation lithography is performed on hydrogen terminated Si(100) using a scanning tunneling microscope, which spatially defined chemically reactive regions. Next, atomic layer deposition of titanium dioxide produces an etch-resistant hard mask pattern on these regions. Reactive ion etching then transfers the mask pattern onto Si with pattern height of 17 nm, critical dimension of approximately 6 nm, and full-pitch down to 13 nm. The effects of linewidth, template atomic defect density, and line-edge roughness are examined in the context of controlling fabrication with arbitrary feature control, suggesting a possible critical dimension down to 2 nm on 10 nm tall features. A metrology standard is demonstrated, where the atomically resolved mask template is used to determine the size of a nanofabricated sample showing a route to image correction. [ABSTRACT FROM AUTHOR]

Abstract  The key challenge to understand the nanomechanical behavior of nanoparticle chain aggregates (NCA) is strongly dependent on accurate determination of the contact area between individual particles. Experimental determination of the contacting radius is extremely difficult and often not reliable. We present calculations based on elastic contact mechanics models, that predict the contact radii of nanoparticles. The model considers important parameters, such as the particle size, the elastic property of the materials and the effect of humidity that intervenes between the contacts. Calculations carried out for four selected materials show that there is a large difference between the radii of contacts formed in vacuum and in ambient conditions. In vacuum, the surface energy of the material is higher compared to that in ambient condition and the contact formation is dominated by the strong interactions between the surfaces. In ambient condition, the contact is dominated by the Laplace pressure due to the condensed water meniscus between the contacts. Calculations presented in this article show that the contact radius between nanoparticles depends on materials properties and the environment. [ABSTRACT FROM AUTHOR]

Atomically precise fabrication has an important role to play in developing atom‐based electronic devices for use in quantum information processing, quantum materials research, and quantum sensing. Atom‐by‐atom fabrication has the potential to enable precise control over tunnel coupling, exchange coupling, on‐site charging energies, and other key properties of basic devices needed for solid‐state quantum computing and analog quantum simulation. Using hydrogen‐based scanning probe lithography, individual dopant atoms are deterministically placed relative to atomically aligned contacts and gates to build single electron transistors, single atom transistors, and gate‐controlled quantum sensing devices. The key steps required to fabricate and demonstrate the essential building blocks needed for spin selective initialization/readout and coherent quantum manipulation are described. [ABSTRACT FROM AUTHOR]