MIT News February 9, 2023 Squeezing of the electromagnetic vacuum is an essential metrological technique used to reduce quantum noise in applications spanning gravitational wave detection, biological microscopy and quantum information science. In superconducting circuits, the resonator-based Josephson-junction parametric amplifiers conventionally used to generate squeezed microwaves are constrained by a narrow bandwidth and low dynamic range. An international team of researchers (USA – MIT, MIT Lincoln Laboratory, industry, Australia) developed a dual-pump, broadband Josephson travelling-wave parametric amplifier that combined a phase-sensitive extinction ratio of 56 dB with single-mode squeezing on par with the best resonator-based squeezers. They demonstrated two-mode squeezing at […]
Category Archives: Quantum technology
When the light is neither ‘on’ nor ‘off’ in the nanoworld
Phys.org February 14, 2023 Plasmon modes are treated as quasiparticles, and they are considered essential for the realization of future nanoscale quantum functionality. Implementing and demonstrating such functionality requires access to the quasiparticle’s quantum state to monitor and manipulate its corresponding quantum wave packet dynamics in Hilbert space. Researchers in Germany succeeded in detecting such superposition states of light directly in a nanostructure using plasmon-assisted electron emission as a signal in coherent two-dimensional nanoscopy. The observation of a quantum coherence oscillating at the third harmonic of the plasmon frequency was traced back to the superposition of energetically non-adjacent plasmon occupation […]
The first lab-created ‘quantum abacus’
Phys.org February 2, 2023 An international team of researchers (UK, Italy) has reported the experimental realization of the prime number quantum potential VN(x), defined as the potential entering the single-particle Schrödinger Hamiltonian with eigenvalues given by the first N prime numbers. Using computer-generated holography, they created light intensity profiles suitable to optically trap ultracold atoms in these potentials for different N values. As a further application, they implemented a potential whose spectrum is given by the lucky numbers, a sequence of integers generated by a different sieve than the familiar Eratosthenes’s sieve used for the primes. According to the researchers their results pave the way […]
Scientists make a quantum harmonic oscillator at room temperature
Phys.org January 12, 2023 Room temperature polariton condensate lattices, suitable candidates for neuromorphic computing and physical simulations of complex problems, have been achieved by nanoimprinting microcavities, which by nature lacks the crucial tunability required for realistic reconfigurable simulators. An international team of researchers (UK, Singapore) has made a quantum harmonic oscillator at room temperature by an on-the-fly fully tunable optical approach. The condensate is delocalised from the excitation region by macroscopic distances, leading both to longer coherence and a threshold one order of magnitude lower than that with a conventional Gaussian excitation profile. They observed different mode selection behaviour compared […]
A diamond-based quantum amplifier
Phys.org December 16, 2022 Artificial quantum systems, based on superconducting circuits, can now amplify and detect even single microwave photons. However, this requires operating at millikelvin temperatures. Natural quantum systems can also be used for low-noise microwave amplification using stimulated emission effects; but they generate a higher noise, especially when operating above ~1 K. Researchers in Israel have demonstrated the use of electron spins in diamond as a quantum microwave amplifier operating with quantum-limited internal noise, even above liquid nitrogen temperatures. They reported on the amplifier’s design, gain, bandwidth, saturation power, and noise. According to the researchers this capability can […]
Imposter physical particles revealed: A key advance for quantum technology
Phys.org December 16, 2022 Hybrid semiconductor–superconductor devices hold great promise for realizing topological quantum computing with Majorana zero modes. However, multiple claims of Majorana detection, based on either tunnelling or Coulomb blockade (CB) spectroscopy, remain disputed. An international team of researchers (Austria, USA – Princeton University, Spain) devised an experimental protocol that allowed them to perform both types of measurement on the same hybrid island by adjusting its charging energy via tunable junctions to the normal leads. This method reduces ambiguities of Majorana detections by checking the consistency between CB spectroscopy and zero-bias peaks in non-blockaded transport. They observed junction-dependent, […]
Using the power of symmetry for new quantum technologies
Phys.org December 15, 2022 In previous research, only one waveguide has been coupled to the qubit with limited access to its symmetries. Researchers in Sweden used two waveguides. They demonstrated a novel coupling scheme between an artificial molecule comprising two identical, strongly coupled transmon qubits and two microwave waveguides. The coupling was engineered so that transitions between states of the same symmetry, with respect to the permutation operator, are predominantly coupled to one waveguide. The coupling selectivity exceeded by a factor of 30 for both waveguides in their device. They showed that it can be used to coherently couple states […]
Scientists construct novel quantum testbed one atom at a time
Phys.org November 29, 2022 A team of researchers in the US (Argonne National Laboratory, Old Dominion University) synthesized artificial graphene nanoribbons by positioning carbon monoxide molecules on a copper surface to confine its surface state electrons into artificial atoms positioned to emulate the low-energy electronic structure of graphene derivatives. They showed that the dimensionality of artificial graphene can be reduced to one dimension with proper “edge” passivation, with the emergence of an effectively gapped one-dimensional nanoribbon structure which showed evidence of topological effects analogous to graphene nanoribbons. They spatially explored robust, zero-dimensional topological states by altering the topological invariants of […]
New theory of electron spin to aid quantum devices
Phys.org November 10, 2022 Researchers at Caltech have developed a new theory and numerical calculations to predict spin decoherence in materials with high accuracy. They adapted a theory of electrical transport to study spin and discovered that this method can capture two main mechanisms governing spin decoherence in materials—spin scattering off atomic vibrations, and spin precession modified by atomic vibrations. They could predict spin decoherence times with an accuracy of a few percent of the measured values—down to a billionth of a second—and access microscopic details of spin motion beyond the reach of experiments. Their research tools—computers and quantum mechanics—can […]
A new method to enable efficient interactions between photons
Phys.org October 6, 2022 Photonics stands out as fundamental to realize the full potential of quantum technology. It provides a modular approach where the main challenges lie in the construction of high-quality building blocks and in the development of methods to interface the modules. In a review article an international team of researchers (France, UK, Canada, Germany, Denmark, South Korea) used the example of quantum dot devices to present the physics of deterministic photon–emitter interfaces, including the main photonic building blocks required to scale up, and discuss quantitative performance benchmarks. While their focus is on quantum dot devices, the presented […]