Instead of measuring directly the system, quantum probes interact with it and are then measured. To avoid such destruction one can use non demolition measurements. For example to count a number of photons usually one would need to convert each photons into an electric signal. One difficulty in quantum optic experiments is to measure a system without destroying it. Press: Cambridge, 1997).Physics Colloquium: Repeated non demolition measurements and wave function collapse Partager cet événement : Leonhardt, U Measuring the Quantum State of Light. Generation and efficient measurement of single photons from fixed-frequency superconducting qubits. Qubit-photon interactions in a cavity: Measurement-induced dephasing and number splitting. Single-shot quantum non-demolition detection of itinerant microwave photons. Iterative maximum-likelihood reconstruction in quantum homodyne tomography. Machine learning for discriminating quantum measurement trajectories and improving readout. Flux-driven Josephson parametric amplifier. Observation of high coherence in Josephson junction qubits measured in a three-dimensional circuit QED architecture. Quantum non-demolition detection of single microwave photons in a circuit. Seeing a single photon without destroying it. Single microwave-photon detector using an artificial Λ-type three-level system. Microwave photon counter based on Josephson junctions. Robust concurrent remote entanglement between two superconducting qubits. Observation of measurement-induced entanglement and quantum trajectories of remote superconducting qubits. Controlled release of multiphoton quantum states from a microwave cavity memory. Microwave-controlled generation of shaped single photons in circuit quantum electrodynamics. Quantum dynamics of an electromagnetic mode that cannot contain N photons. Deterministically encoding quantum information using 100-photon Schrödinger cat states. Synthesizing arbitrary quantum states in a superconducting resonator. Cavity-based quantum networks with single atoms and optical photons.

Nondestructive detection of an optical photon. Quantum nondemolition detection of a propagating microwave photon. Quantum nondemolition photon detection in circuit QED and the quantum Zeno effect. Quantum non-demolition measurements in optics. Quantum nondemolition measurement of the photon number via the optical Kerr effect. A scheme for efficient quantum computation with linear optics. Single-photon detectors for optical quantum information applications. Our scheme can serve as a building block for quantum networks connecting distant qubit modules as well as a microwave-photon-counting device for multiple-photon signals. Using the entanglement and the high-fidelity qubit readout, we demonstrate a QND detection of a single photon with the quantum efficiency of 0.84 and the photon survival probability of 0.87. Here, we implement a deterministic entangling gate between a superconducting qubit and an itinerant microwave photon reflected by a cavity containing the qubit. However, the counterpart for microwaves has been elusive despite the recent progress in microwave quantum optics using superconducting circuits 13, 14, 15, 16, 17, 18, 19. The long-sought QND detection of a flying photon was recently demonstrated in the optical domain using a single atom in a cavity 11, 12. This is in stark contrast to conventional photon detectors 2 that absorb a photon to trigger a ‘click’. Of particular interest is a quantum non-demolition (QND)-type detector, which projects an electromagnetic wave onto the photon-number basis 6, 7, 8, 9, 10.

Photon detectors are an elementary tool to measure electromagnetic waves at the quantum limit 1, 2 and are heavily demanded in the emerging quantum technologies such as communication 3, sensing 4 and computing 5.

Demolition physics