Phys.org October 13, 2021 Calculating quantum light-matter takes enormous amounts of time and computing power—it also becomes very cumbersome. An international team of researchers (Germany, Sweden, Austria) has found a simple way to circumvent this problem by reshaping the equation so that the material part itself accounts for the quantum mechanical uncertainty of the light, far fewer additional photons are needed to describe the combined system of quantum light and matter. The new approach can capture most features of this extreme limit without the need to consider any photon at all. Adding just a few photons is enough to provide […]
Tag Archives: Quantum technologies
Combining two approaches to advance quantum computing
Phys.org July 26, 2021 An international team of researchers (USA – Yale University, the Netherland, Spain, Denmark, Sweden) experimentally demonstrated a new qubit that fuses the electromagnetic modes of superconducting circuits and the spins of small numbers of electrons trapped in semiconductor quantum dots. They were able to show how to harness this spin-dependent supercurrent to achieve both spin detection and coherent spin manipulation. The work represents a significant advancement to our understanding and control of Andreev levels which are microscopic, electronic states that exist in all Josephson junctions. In superconductor-semiconductor heterostructures such as the nanowire junctions investigated in this […]
Combining classical and quantum computing opens door to new discoveries
Science Daily June 15, 2021 Variational quantum eigensolvers (VQEs) combine classical optimization with efficient cost function evaluations on quantum computers. An international team of researcher (Canada, Austria, Germany) proposed a new approach to VQEs using the principles of measurement-based quantum computation. This strategy uses entangled resource states and local measurements. They have presented two measurement based VQE schemes. The first introduces a new approach for constructing variational families. The second provides a translation of circuit to measurement-based schemes. Both schemes offer problem-specific advantages in terms of the required resources and coherence times. The algorithm offers high error tolerance, often an […]
Quantum sensing: Odd angles make for strong spin-spin coupling
Science Daily May 25, 2021 Exotic quantum vacuum phenomena are predicted in cavity quantum electrodynamics systems with ultra-strong light-matter interactions. However, such predictions have not been realized because antiresonant interactions are typically negligible compared to resonant interactions in light-matter systems. An international team of researchers (USA – Rice University, Japan, Germany, China) reports an unusual, ultra-strongly coupled matter-matter system of magnons that is analytically described by a unique Hamiltonian in which the relative importance of resonant and antiresonant interactions can be easily tuned and the latter can be made vastly dominant. They found a regime where vacuum Bloch-Siegert shifts, the […]
First Photonic Quantum Computer on the Cloud
IEEE Spectrum September 9, 2020 A Canadian company working with their US partners has made a quantum computing platform publicly available. Applicants can access 8, 12, and soon 24 qubit machines over the cloud. In the coming months, the company will release a blueprint for photonic quantum computing that is essentially a primer on how to scale to millions of qubits in a fault-tolerant manner. They use continuous variable quantum computing which relies on “squeezed states” consisting of superpositions of multiple photons. Squeezed states take advantage of Heisenberg’s uncertainty principle reducing the uncertainty in the measurements of a given variable […]
A molecular approach to quantum computing
Science Daily September 2, 2020 Researchers in the US (Caltech) applied the concept of error correction to rotating molecules in superposition. If the orientation or angular momentum of the molecule shifts by a small amount, those shifts can be simultaneously corrected. They constructed quantum error-correcting codes that embed a finite-dimensional code space in the infinite-dimensional Hilbert space of rotational states of a rigid body. They protect against both drift in the body’s orientation and small changes in its angular momentum. Hence, they may be well suited for robust storage and coherent processing of quantum information. They have described codes and […]
Researchers manipulate two bits in one atom
Phys.org September 1, 2020 An international team of researchers (the Netherlands, Chile, Spain) has shown that it is possible to gain independent access to both the spin and orbital degrees of freedom of a single atom, inciting and probing excitations of each moment. By coordinating a single Fe atom atop the nitrogen site of the Cu2N lattice, they created a single-atom system with a large zero-field splitting and an unquenched uniaxial orbital moment that closely approaches the free-atom value. They demonstrated a full reversal of the orbital moment through a single-electron tunneling event between the tip and Fe atom, a […]
Revolutionary quantum breakthrough paves way for safer online communication
Phys.org September 2, 2020 An international team of researchers (UK, Austria, Croatia) used multiplexing which splits the light particles, emitted by a single system, so they can be received by multiple users efficiently. They designed a network for eight users using just eight receiver boxes As the user numbers grow, the logistics become increasingly unviable—for instance 100 users would take 9,900 receiver boxes. To demonstrate its functionality across distance the receiver boxes were connected to optical fibres via different locations across Bristol. The ability to transmit messages via quantum communication was tested using the city’s existing optical fibre network. The […]
Quantum leap: Photon discovery is a major step toward at-scale quantum technologies
EurekAlert May 20, 2020 Architectures for photonic quantum computing place stringent demands on high quality information carriers. An international team of researchers (UK, Italy) has fabricated on-chip photon sources and demonstrated that they meet the computing requirements. The photon sources are fabricated in silicon using mature processes and exploit a dual-mode pump-delayed excitation scheme to engineer the emission of spectrally pure photon pairs through inter-modal spontaneous four-wave mixing in low-loss spiraled multi-mode waveguides. They measured a spectral purity of 0.9904 ± 0.0006, a mutual indistinguishability of 0.987 ± 0.002, and >90% intrinsic heralding efficiency and on-chip quantum interference with a visibility of 0.96 ± 0.02 between […]
Unlocking promising properties to create future technologies
EurekAlert April 30, 2020 The manifestation of quantization in macroscopic physical systems has showcased important quantum phenomena, such as quantized conductance in (fractional) quantum Hall effects and quantized vortices in superconductors. An international team of researchers (USA – Rensselaer Polytechnic Institute, Florida State University, UT Dallas, Arizona State University, Japan, Hong Kong) reported the experimental observation of quantized exciton energies in a macroscopic system with strong Coulomb interaction, monolayer WSe2 crystal under a strong magnetic field. This work demonstrates the optical version of the QHE for excitons, and the researchers believe it will open the door for further discovery and […]