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Quantum metrology uses quanta — individual packets of energy — for setting the standards that define units of measurement and for other high-precision research. Quantum mechanics sets the ultimate limit on the accuracy of any measurement. Quantum metrology, therefore, uses quantum effects to enhance precision beyond that possible through classical approaches.
The ability to characterize large and complex nuclear-spin networks could enable quantum applications, such as quantum simulations of many-body physics. Here the authors develop a high-resolution quantum-sensing method and use it to image a network of 50 nuclear spins surrounding a single NV center in diamond.
In order to explore superconductivity in hydride materials, local magnetometry inside a diamond anvil cell is performed with sub-micron spatial resolution at megabar pressures using nitrogen-vacancy colour centres.
A room-temperature demonstration of optomechanical squeezing of light and measurement of mechanical motion approaching the Heisenberg limit using a phononic-engineered membrane-in-the-middle cavity with ultralow noise.
Quantum technologies change our notion of measurement. Chenyu Wang elaborates on how quantum squeezing enhances the precision of gravitational-wave interferometers.
Optical atomic clocks are extremely accurate sensors despite the poor use of their resources. A parallel quantum control approach might help to optimize the resources of optical atomic clocks, which could lead to an exponential improvement in their performance.
In principle, quantum entanglement gives advantages in radar detection even under noisy and lossy operating conditions. More than a decade after the proposal, the predicted quantum advantage has finally been demonstrated at microwave frequencies.
Controlling the spatial distribution of optically active spin defects in solids is a long-standing goal in the quantum sensing and simulation communities. Measurements of the many-body noise generated by the spins were used to verify that a highly coherent and strongly interacting quantum spin system was confined to two dimensions within a diamond substrate.
Two superconductors connected by a weak link form a Josephson junction, a nonlinear circuit element at the heart of many quantum devices. Quantized electrical current steps that were predicted decades ago have now been observed experimentally.
‘Squeezing’ of light can be used to alter the distribution of quantum noise to benefit quantum sensing and other applications. An improved design for a microwave photon squeezer provides high performance over a large bandwidth.