Phys.org March 4, 2024 The coherence time of the quantum system surpasses that of the oscillator probing the system. Correlation spectroscopy overcomes this limitation by probing two quantum systems with the same noisy oscillator for a measurement of their transition frequency difference enabling very precise comparisons of atomic clocks. An international team of researchers (Austria, Israel, USA – Caltech) extended correlation spectroscopy to the case of multiple quantum systems undergoing strong correlated dephasing. They modelled Ramsey correlation spectroscopy with N particles as a multiparameter phase estimation problem and demonstrated that multiparticle correlations could assist in reducing the measurement uncertainties even […]
Tag Archives: Quantum sensors
Breakthrough paves way for photonic sensing at the ultimate quantum limit
Phys.org June 6, 2022 Quantum states of light have been shown to enhance precision in absorption estimation over classical strategies. However, most quantum sensing schemes rely on special entangled or squeezed states of light or matter that are hard to generate and detect. Researchers in the UK have shown it is possible to perform high precision measurements of important physical properties without the need for sophisticated quantum states of light and detection schemes. The key to this breakthrough is the use of ring resonators that guide light in a loop and maximize its interaction with the sample under study. Importantly, […]
Scientists turn a hydrogen molecule into a quantum sensor
Science Daily April 22, 2022 Researchers at UC Irvine positioned two bound atoms of hydrogen in between the silver tip of the scanning tunneling microscope (STM) and a sample composed of a flat copper surface arrayed with small islands of copper nitride. With pulses of the laser lasting trillionths of a second, they were able to excite the hydrogen molecule and detect changes in its quantum states at cryogenic temperatures and in the ultrahigh vacuum environment of the instrument, rendering atomic-scale, time-lapsed images of the sample. The STM was equipped to detect minute electrical current flowing in this space and […]
Physicists create compressible optical quantum gas
Phys.org March 24, 2022 The compressibility of a medium, quantifying its response to mechanical perturbations is a fundamental property determined by the equation of state. For gases of material particles studies of the mechanical response are well established in fields from classical thermodynamics to cold atomic quantum gases. Researchers in Germany demonstrated the measurement of the compressibility of a two-dimensional quantum gas of light in a box potential and obtained the equation of state for the optical medium. The experiment was carried out in a nanostructured dye-filled optical microcavity. They observed signatures of Bose-Einstein condensation at high phase-space densities in […]
Cooling matter from a distance
Science Daily February 2, 2022 Researchers in Switzerland succeeded in forming a control loop consisting of two quantum systems separated by one meter. Within this loop a vibrating membrane was cooled by a cloud of atoms, and the two systems were coupled to one another by laser light. As one of the systems acts as a control unit for the other, no measurement is needed. Instead, the control system is configured to bring the target system into a desired state by means of coherent quantum mechanical interaction. They successfully used this coherent feedback mechanism to reduce the temperature of the […]
Detecting hidden signals
EurekAlert March 25, 2021 The field of quantum sensing has shown a lot of potential for detecting very small signals. However, the ability to truly optimize these sensors has been thwarted by the complexity of control schemes. A team of researchers in the US (Johns Hopkins University, University of Maryland) applied filter functions and optimal quantum control theories to a use case of qubit sensors that mirror a classic problem in signal detection theory: optimal detection of a known signal from background noise with a controllable quantum sensor. They obtained analytical insight into the optimal control protocol when the background […]
Analysis paves way for more sensitive quantum sensors
Nanowerk November 16, 2020 Researchers at the University of Chicago proposed creating a string of photonic cavities, where photons can be transported to adjacent cavities. Such a string could be used as a quantum sensor. By harnessing non-Hermitian dynamics, where dissipation leads to interesting consequences, they were able to calculate that a string of these cavities would increase the sensitivity of the sensor much more than the number of cavities added. In fact, it would increase the sensitivity exponentially in system size. To prove the theory, they are building a network of superconducting circuits that can move photons between cavities. […]
Laser loop couples quantum systems over a distance
Science Daily May 7, 2020 An international team of researchers (Switzerland, Germany) used laser light to couple the vibrations of a 100 nanometer thin membrane to the motion of the spin of atoms over a distance of one meter. As a result, each vibration of the membrane sets the spin of the atoms in motion and vice versa. In this laser loop, the properties of the light can be controlled such that no information about the motion of the two systems is lost to the environment, thus ensuring that the quantum mechanical interaction is not disturbed. It is possible to […]
A spookily good sensor
Phys.org February 19, 2020 Researchers in Japan placed a millimeter-sized sphere of yttrium iron garnet in the same resonant cavity as a superconducting Josephson junction qubit, which acted as the sensor. Because of the coupling of the sphere to resonant cavity, and, in turn, between the cavity to the qubit, the qubit could only be excited by an electromagnetic pulse if no magnetic excitations were present in the sphere. Reading the state of the qubit then reveals the state of the sphere. By using single-shot detection instead of averaging, they were able to make the device both highly sensitive and […]
Honing quantum sensing
MIT News September 25, 2018 Extreme sensitivity of quantum sensors to their surrounding environment creates the vexing problem of environmental noise in quantum sensor systems. A team of researchers in the US (MIT, Yale University) has developed an approach that is complementary to existing Dynamical decoupling and established error-corrected quantum sensing (ECQS) methods. This approach allows frequency-independent filtering, because it exploits spatial rather than temporal noise correlations. The new ECQS scheme makes use of noise correlations at different positions in a quantum sensor. In this way, the new approach can tell signal from noise even in the common case where […]