MIT News February 21, 2023 To overcome errors in the qubits due to heat in quantum systems, researchers at MIT developed a wireless communication system that enables a quantum computer to send and receive data to and from electronics outside the refrigerator using high-speed terahertz waves. A transceiver chip, cryostat, placed inside the fridge sends and receives data from a terahertz wave source outside the cryostat using backscatter. An array of antennas on top of the chip, each of which is only about 200 micrometers in size, act as tiny mirrors. These mirrors can be “turned on” to reflect waves […]
Category Archives: Quantum computing
New spin control method brings billion-qubit quantum chips closer
Phys.org January 12, 2023 The electron spin forms a qubit that is naturally robust to electric fluctuations. However, a common control strategy is the integration of micromagnets to enhance the coupling between spins and electric fields, which, in turn, hampers noise immunity and adds architectural complexity. An international team of researchers (Australia, Japan, Germany, Canada) used switchable interaction between spins and orbital motion of electrons in silicon quantum dots, without a micromagnet. The weak effects of relativistic spin–orbit interaction in silicon were enhanced, leading to a speed up in Rabi frequency by a factor of up to 650 by controlling […]
Physicists Discover a New Way to ‘See’ Objects Without Looking at Them
Science Alert December 29, 2022 Instead of lasers and mirrors, researchers in Finland proposed the concept of coherent interaction-free detection and demonstrated it experimentally using a three-level superconducting transmon circuit to detect an electromagnetic wave pulsed into a chamber. They showed that it is possible to ascertain the presence of a microwave pulse resonant with the second transition of the transmon, while at the same time avoid exciting the device onto the third level. Experimentally, this was done by using a series of Ramsey microwave pulses coupled into the first transition and monitoring the ground-state population. The protocol can be […]
New instrument measures supercurrent flow; data has applications in quantum computing
Phys.org December 5, 2022 To understand the inner workings of quantum computing and enable supercomputing a team of researchers in the US (Iowa State University, University of Alabama at Birmingham, University of Wisconsin-Madison, Madison, Florida State University, Ames National Laboratory) built a Cryogenic Magneto-Terahertz Scanning Near-field Optical Microscope (cm-SNOM). It comprises three main equipment: i) a 5 T split pair magnetic cryostat with a custom made insert for mounting SNOM inside; ii) an atomic force microscope (AFM) unit that accepts ultrafast THz excitation and iii) a MHz repetition rate, femtosecond laser amplifier for high-field THz pulse generation and sensitive detection. […]
Universal parity quantum computing, a new architecture that overcomes performance limitations
Phys.org October 28, 2022 Researchers in Austria have developed a universal gate set for quantum computing with all-to-all connectivity and intrinsic robustness to bit-flip errors based on parity encoding. They showed that logical controlled phase gate and Rz rotations can be implemented in parity encoding with single-qubit operations. Together with logical Rx rotations, implemented via nearest-neighbor controlled-NOT gates and an Rx rotation, these form a universal gate set. As the controlled phase gate requires only single-qubit rotations, the proposed scheme has advantages for several cornerstone quantum algorithms, e.g., the quantum Fourier transform. They presented a method to switch between different […]
A molecular multi-qubit model system for quantum computing
Phys.org October 13, 2022 An international team of researchers (UK, Italy) developed a molecular model system with several separate qubit units, which can be spectroscopically detected and the states of which can be switched by interacting with one another. They used pulsed Electron Paramagnetic Resonance (EPR) techniques to characterize and separately address the individual electron spin qubits; CuII, Cr7Ni ring and a nitroxide, and to determine the strength of the inter-qubit dipolar interaction. Orientation selective Relaxation-Induced Dipolar Modulation Enhancement (os-RIDME) detecting across the CuII spectrum revealed a strongly correlated CuII-Cr7Ni ring relationship; detecting on the nitroxide resonance measured both the […]
Why ‘erasure’ could be key to practical quantum computing
Phys.org September 1, 2022 The fundamental challenge to quantum computers is that the operations are noisy. Rather than focusing solely on reducing the number of errors a team of researchers in the US (Yale University, University of Wisconsin-Madison, Princeton) made errors more visible. They delved deeply into the actual physical causes of error and engineered their system so that the most common source of error effectively eliminates, rather than simply corrupting, the damaged data leading to “erasure error,” which is fundamentally easier to weed out than data that is corrupted but still looks like all the other data. Erasure errors […]
Record-Breaking Experiment Could Solve a Huge Challenge in Quantum Computing
Science Alert August 8, 2022 Strong interactions between two single atoms have not been harnessed for ultrafast quantum operations due to the stringent requirements on the fluctuation of the atom positions and the necessary excitation strength. Researchers in Japan have developed a technique to trap and cool atoms to the motional quantum ground state of holographic optical tweezers, which allows control of the inter-atomic distance down to 1.5 μm with a quantum-limited precision of 30 nm. Then they used ultrashort laser pulses to excite a pair of these nearby atoms far beyond the Rydberg blockade regime and performed Ramsey interferometry with attosecond […]
A roadmap for the future of quantum simulation
Phys.org July 29, 2022 Many of the most promising short-term applications of quantum computers fall under the umbrella of quantum simulation: modelling the quantum properties of microscopic particles that are directly relevant to modern materials science, high-energy physics, and quantum chemistry. This would impact several important real-world applications, such as developing materials for batteries, industrial catalysis or nitrogen fixing. Quantum simulation can be performed not only on future fault-tolerant digital quantum computers but also through special-purpose analogue quantum simulators. An international team of researchers (UK, Germany, Austria, USA – industry) has provided an overview of the state of the art […]
Discovery of the one-way superconductor, thought to be impossible
Nanowerk April 27, 2022 Showing magnetic-field-free, single-directional superconductivity with Josephson coupling, it would serve as the building block for next-generation superconducting circuit technology. An international team of researchers (Germany, China, the Netherlands, USA – Princeton University, Johns Hopkins University) has fabricated an inversion symmetry breaking van der Waals heterostructure of NbSe2/Nb3Br8/NbSe2. They demonstrated that even without a magnetic field, the junction can be superconducting with a positive current while being resistive with a negative current. The ΔIc behaviour (the difference between positive and negative critical currents) with magnetic field is symmetric and Josephson coupling is proved through the Fraunhofer pattern. […]