Science Alert June 22, 2022 Researchers in Australia have created a functional quantum processor and tested it by modeling a small molecule in which each atom has multiple quantum states. They used a scanning tunneling microscope in an ultra-high vacuum to place quantum dots with sub-nanometer precision. The trickiest parts were figuring out: exactly how many atoms of phosphorus should be in each quantum dot; exactly how far apart each dot should be; and then engineering a machine that could place the tiny dots in exactly the right arrangement inside the silicon chip. The final quantum chip contained 10 quantum […]
Category Archives: Quantum computers
Using two different elements creates new possibilities in hybrid atomic quantum computers
Nanowerk March 2, 2022 Researchers at the University of Chicago have introduced a dual-element atom array with individual control of single rubidium and cesium atoms. They were placed in arrays with up to 512 trapping sites and observed negligible crosstalk between the two elements. Furthermore, by continuously reloading one atomic element while maintaining an array of the other, they demonstrated a new continuous operation mode for atom arrays without any off-time. According to the researchers the results enable avenues for auxiliary-qubit-assisted quantum protocols such as quantum nondemolition measurements and quantum error correction, as well as continuously operating quantum processors and […]
Researchers propose a simpler design for quantum computers
Phys.org November 29, 2021 It is challenging to construct large numbers of gates for photons and connect them in a reliable fashion to perform complex calculations. Researchers at Stanford University have proposed a scalable architecture for a photonic quantum computer using readily available components – a fiber optic cable, a beam splitter, a pair of optical switches and an optical cavity, and the size of the machine doesn’t increase with the size of the quantum program you want to run. The design consists of two main sections – a storage ring and a scattering unit. The storage ring is a fiber […]
Shrinking qubits for quantum computing with 2D materials
Nanowerk December 1, 2021 The capacitor electrodes that comprise the qubits in quantum computers must be large to avoid lossy dielectrics. This hinders scaling degrading individual qubit addressability and limiting the spatial density of qubits. An international team of researchers (USA – Columbia University, Raytheon BBN Technologies, Japan) took advantage of the unique properties of van der Waals (vdW) materials to reduce the qubit area by >1000 times while preserving the capacitance while maintaining quantum coherence. The qubits combine conventional aluminum-based Josephson junctions with parallel-plate capacitors composed of crystalline layers of superconducting niobium diselenide and insulating hexagonal boron nitride. The […]
How a novel radio frequency control system enhances quantum computers
Phys.org November 9, 2021 Researchers at the Lawrence Berkeley National Laboratory have demonstrated a new way to control qubits by substituting the larger, more costly traditional RF control systems with smaller interactive mixing modules. The modular system has high -reliability, delivering high-resolution, low-noise RF signals needed to manipulate and measure the superconducting qubit at room temperature. To do so, they shifted the qubit manipulation and measurement signal frequency between the electronics baseband and the quantum system. According to the researchers their system could be expanded to other quantum information science platforms, and RF mixing can be expanded to higher frequencies. […]
Graphene valleytronics: Paving the way to small-sized room-temperature quantum computers
Phys.org September 8, 2021 Electrons in two-dimensional hexagonal materials have an extra degree of freedom that can be used to encode and process quantum information. An international team of researchers (India, Germany) demonstrated that both valley-selective excitation and valley-selective high-harmonic generation can be achieved in pristine graphene by using a combination of two counter-rotating circularly polarized fields, the fundamental and its second harmonic. Controlling the relative phase between the two colors allowed them to select the valleys where the electron–hole pairs and higher-order harmonics are generated. They described an all-optical method for measuring valley polarization in graphene with a weak […]
Engineers make critical advance in quantum computer design
Phys.org August 13, 2021 Advancing from the current few-qubit devices to silicon quantum processors with upward of a million qubits, as required for fault-tolerant operation, presents several unique challenges, one of the most demanding being the ability to deliver microwave signals for large-scale qubit control. Researchers in Australia have demonstrated a potential solution to this problem by using a three-dimensional dielectric resonator to broadcast a global microwave signal across a quantum nanoelectronic circuit. The technique uses only a single microwave source and can deliver control signals to millions of qubits simultaneously. They have shown that the global field can be […]
Rare open-access quantum computer now operational
EurekAlert March 15, 2021 Scientists worldwide can use ion-based testbed at Sandia National Laboratories QSCOUT for research that might not be possible at their home institutions, without the cost or restrictions of using a commercial testbed. QSCOUT serves a need in the quantum community by gives users an uncommon amount of control over their research, opportunity to study the machine itself, which are not yet available in commercial quantum computing systems. It also saves theorists and scientists from the trouble of building their own machines. Sandia hopes to gain new insights into quantum performance and architecture as well as solve […]
A new strategy to implement a high-fidelity mixed-species entangling gate
Phys.org September 22, 2020 One of the greatest challenges in the development of trapped ion quantum computers is scalability because adding new qubits to a quantum computing system often results in a rapid decrease in performance, as it introduces new errors and makes it harder to interact with a single qubit without affecting some of the others. Researchers in the UK used modularization and optical networking to have ions in separate ion traps and vacuum systems, which are only connected through optical fibers. This approach limits crosstalk between qubits, retaining only interactions that are desirable and can be controlled by […]
NIST scientists create new recipe for single-atom transistors
EurekAlert May 11, 2020 Using a room temperature grown locking layer and precise control over the entire fabrication process, a team of researchers in the US (NIST, University of Maryland) reduced unintentional dopant movement while achieving high quality epitaxy in scanning tunneling microscope (STM)-patterned devices. They demonstrated the exponential scaling of the tunneling resistance on the tunnel gap as it is varied from 7 dimer rows to 16 dimer rows, 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 […]