Phys.org September 2, 2024 A quantum emitter interacting with photons in a single optical mode constitutes a one-dimensional atom. A coherent and efficiently coupled one-dimensional atom provides a large nonlinearity, enabling photonic quantum gates. Achieving a high coupling efficiency ( factor) and low dephasing is challenging. An international team of researchers (Switzerland, Germany) used a semiconductor quantum dot in an open microcavity as an implementation of a one-dimensional atom. With a weak laser input, they achieved an extinction of 99.2% in transmission and a concomitant bunching in the photon statistics, showcasing the reflection of the single-photon component and the transmission […]
Category Archives: Quantum computer
Toward a code-breaking quantum computer
MIT News August 23, 2024 Researchers at MIT made two improvements to Regev’s quantum factoring algorithm by addressing its space efficiency and its noise-tolerance. They improved the quantum space efficiency of Regev’s algorithm by constructing a quantum factoring circuit using O(n log n) qubits and O(n3/2log n) gates. achieving the best of Shor and Regev gates. Optimization was achieved by implementing efficient and reversible exponentiation with Fibonacci numbers in the exponent, rather than the usual powers of 2. This technique allowed them to perform quantum modular exponentiation that was efficient in both space and size without requiring significant precomputation, a […]
A new design for quantum computers
Science Daily February 15, 2024 Arrays of Rydberg atoms are suitable to study quantum phase transitions in one dimension. Theoretically predicted chiral transition out of period-four phase is still pending experimental verification mainly due to extremely short interval over which this transition is realized in a single-component Rydberg array. Researchers in the Netherlands showed that multicomponent Rydberg arrays with extra experimentally tunable parameters provided a mechanism to manipulate quantum critical properties without breaking translation symmetry explicitly. They considered an effective blockade model of two component Rydberg atoms. Weak and strong components obeyed nearest- and next-nearest-neighbor blockades correspondingly. When laser detuning […]
A simpler way to connect quantum computers
Science Daily August 30, 2023 Recently, there has been significant interest in rare earth ions, in particular Er3+ for its telecom band optical transition that allows long-distance transmission in optical fibres. However, the development of repeater nodes based on rare earth ions has been hampered by optical spectral diffusion, precluding indistinguishable single-photon generation. Researchers at Princeton University implanted Er3+ into CaWO4 to realize significantly reduced optical spectral diffusion. For shallow implanted ions coupled to nanophotonic cavities with large Purcell factor, they observed single-scan optical linewidths of 150 kHz and long-term spectral diffusion of 63 kHz, both close to the Purcell-enhanced radiative linewidth […]
‘Toggle switch’ can help quantum computers cut through the noise
Science Daily June 26, 2023 Qubits in cavity quantum electrodynamic (QED) architectures are often operated in the dispersive regime, in which the operating frequency of the cavity depends on the energy state of the qubit, and vice versa. The ability to tune these dispersive shifts provides additional options for performing either quantum measurements or logical manipulations. A team of researchers in the US (NIST- Boulder,CO, UMass Amherst, UMass Lowell, Raytheon, MA) coupled two transmon qubits to a lumped-element cavity through a shared superconducting quantum interference device (SQUID). The design balanced the mutual capacitive and inductive circuit components so that both […]
Qubits put new spin on magnetism: Boosting applications of quantum computers
Science Daily March 17, 2023 Unveiling the fundamental dynamics of naturally or artificially formed magnetic quasicrystals in the presence of an external magnetic field remains a difficult problem that may have implications for the design of information processing devices. Researchers at Los Alamos National Laboratory embedded a qubit magnetic Penrose quasicrystal into a quantum annealer to reproduce the formation of magnetic phases driven by specific physical parameter selections. It allowed them to distinguish a wide range of frustrated magnetic configurations at the single-spin scale. They observed some spins dynamically activate, while others remained static, all within an average magnetization space […]
A new method for quantum computing
Phys.org January 31, 2022 Using trapped-ion platform and optical tweezers researchers in the Netherlands have constructed new building blocks for quantum computing that pose fewer technical difficulties than current state-of-the art methods. Since the electric field allows for long-range qubit-qubit interactions mediated by the center-of-mass motion of the ion crystal alone, it is inherently scalable to large ion crystals. The proposed scheme does not rely on ground-state cooling. They studied the effects of imperfect cooling of the ion crystal, as well as the role of unwanted qubit-motion entanglement, and discuss the prospects of implementing the state-dependent tweezers in the laboratory… […]
Scientists simulate ‘fingerprint’ of noise on quantum computer
Phys.org January 26, 2022 Traditionally, noise on the quantum device is characterized directly through qubit and gate measurements, but this approach has drawbacks as it does not adequately capture the effect of noise on realistic multi-qubit applications. A team of researchers in the US (University of Chicago, Purdue University) simulated the relaxation of stationary quantum states on a quantum computer to obtain a unique spectroscopic fingerprint of the computer’s noise. In contrast to traditional approaches, they obtained the frequency profile of the noise as it is experienced by the simulated stationary quantum states. Data from multiple superconducting-qubit IBM processors shows […]
Light meets superconducting circuits
EurekAlert May 10, 2021 Realizing the full potential of quantum computers requires a significant increase in the number of qubits to store and manipulate quantum information. To prevent contaminating quantum signals by thermal noise, the superconducting quantum systems must operate at ultra-low temperatures. An international team of researchers (Switzerland, India) has developed a novel approach that uses light to read out superconducting circuits. They replaced low-noise high-electron mobility transistors and coaxial cables with a lithium niobate electro-optical phase modulator and optical fibers. Microwave signals from superconducting circuits modulate a laser carrier and encode information on the output light at cryogenic […]
Optical fiber could boost power of superconducting quantum computers
Science Daily March 24, 2021 In superconducting quantum processors, each qubit is individually addressed with microwave signal lines that connect room-temperature electronics to the cryogenic environment of the quantum circuit. The complexity and heat load associated with the multiple coaxial lines per qubit limits the maximum possible size of a processor to a few thousand qubits. A team of researchers in the US (NIST, Boulder CO, University of Colorado) has introduced a photonic link using an optical fibre to guide modulated laser light from room temperature to a cryogenic photodetector, capable of delivering shot-noise-limited microwave signals directly at millikelvin temperatures. […]