Quantum state tomography with non-instantaneous measurements, imperfections and decoherence

Tomography of a quantum state is usually based on positive operator-valued measure (POVM) and on their experimental statistics. Among the available reconstructions, the maximum-likelihood (MaxLike) technique is an efficient one. We propose an extension of this technique when the measurement process cannot be simply described by an instantaneous POVM. Instead, the tomography relies on a set of quantum trajectories and their measurement records. This model includes the fact that, in practice, each measurement could be corrupted by imperfections and decoherence, and could also be associated with the record of continuous-time signals over a finite amount of time. The goal is then to retrieve the quantum state that was present at the start of this measurement process. The proposed extension relies on an explicit expression of the likelihood function via the effective matrices appearing in quantum smoothing and solutions of the adjoint quantum filter. It allows to retrieve the initial quantum state as in standard MaxLike tomography, but where the traditional POVM operators are replaced by more general ones that depend on the measurement record of each trajectory. It also provides, aside the MaxLike estimate of the quantum state, confidence intervals for any observable. Such confidence intervals are derived, as the MaxLike estimate, from an asymptotic expansion of multi-dimensional Laplace integrals appearing in Bayesian Mean estimation. A validation is performed on two sets of experimental data: photon(s) trapped in a microwave cavity subject to quantum non-demolition measurements relying on Rydberg atoms; heterodyne fluorescence measurements of a superconducting qubit.Comment: 11 pages, 4 figures, submitte

Exponential convergence of a dissipative quantum system towards finite-energy grid states of an oscillator

Based on the stabilizer formalism underlying Quantum Error Correction (QEC), the design of an original Lindblad master equation for the density operator of a quantum harmonic oscillator is proposed. This Lindblad dynamics stabilizes exactly the finite-energy grid states introduced in 2001 by Gottesman, Kitaev and Preskill for quantum computation. Stabilization results from an exponential Lyapunov function with an explicit lower-bound on the convergence rate. Numerical simulations indicate the potential interest of such autonomous QEC in presence of non-negligible photon-losses.Comment: Submitted, 15 pages, 1 figure

Advanced Planning and Scheduling system: An overview of gaps and potential sample solutions

13 pagesInternational audienceThis paper intends to take up an overview of gaps existing in Advanced Planning Scheduling system (APS). Even if APS system provide a number of solution approaches for several practical problems (inventory and global costs reduction, customer service level increase, pertinent decision making), improvement ways still emerge. Firstly, we have led a functional analysis, to identify some gaps about supply chain management activities (financial aspect and Engineering To Order concept). Then, we made a literature review to identify works have been done in these areas. This review allowed us to outline a second kind of weakness liked to the functional range of some modules too (demand forecasting, proposition of lots sizing, reactivity). So, gaps and potential solutions proposed in the scientist literature, are presented in this paper. We conclude by underlining another type of problem, concerning the management needed to install correctly an APS system

Advanced Planning and Scheduling system: An overview of gaps and potential sample solutions

This paper intends to take up an overview of gaps existing in Advanced Planning Scheduling system (APS). Even if APS system provide a number of solution approaches for several practical problems (inventory and global costs reduction, customer service level increase, pertinent decision making), improvement ways still emerge. Firstly, we have led a functional analysis, to identify some gaps about supply chain management activities (financial aspect and Engineering To Order concept). Then, we made a literature review to identify works have been done in these areas. This review allowed us to outline a second kind of weakness liked to the functional range of some modules too (demand forecasting, proposition of lots sizing, reactivity). So, gaps and potential solutions proposed in the scientist literature, are presented in this paper. We conclude by underlining another type of problem, concerning the management needed to install correctly an APS system.Advanced Planning and Scheduling system, Supply Chain Management, APS gaps, functional analysis

Detection of Skin Disbond in Honeycombs and Coating Detachment by Laser Tapping Technique

Peer reviewed: YesNRC publication: Ye

Applications of Laser-Ultrasonics and Laser Tapping to Aerospace Composite Structures

Peer reviewed: YesNRC publication: Ye

Laser-ultrasonic and laser-tapping techniques for probing aerospace composite structures

Peer reviewed: YesNRC publication: Ye

Quantum control of a cat-qubit with bit-flip times exceeding ten seconds

Binary classical information is routinely encoded in the two metastable states of a dynamical system. Since these states may exhibit macroscopic lifetimes, the encoded information inherits a strong protection against bit-flips. A recent qubit - the cat-qubit - is encoded in the manifold of metastable states of a quantum dynamical system, thereby acquiring bit-flip protection. An outstanding challenge is to gain quantum control over such a system without breaking its protection. If this challenge is met, significant shortcuts in hardware overhead are forecast for quantum computing. In this experiment, we implement a cat-qubit with bit-flip times exceeding ten seconds. This is a four order of magnitude improvement over previous cat-qubit implementations, and six orders of magnitude enhancement over the single photon lifetime that compose this dynamical qubit. This was achieved by introducing a quantum tomography protocol that does not break bit-flip protection. We prepare and image quantum superposition states, and measure phase-flip times above 490 nanoseconds. Most importantly, we control the phase of these superpositions while maintaining the bit-flip time above ten seconds. This work demonstrates quantum operations that preserve macroscopic bit-flip times, a necessary step to scale these dynamical qubits into fully protected hardware-efficient architectures

Laser-Ultrasonic Evaluation of Thermal Spray Coatings

Peer reviewed: YesNRC publication: Ye

Structural determinants of specific DNA-recognition by the THAP zinc finger

Human THAP1 is the prototype of a large family of cellular factors sharing an original THAP zinc-finger motif responsible for DNA binding. Human THAP1 regulates endothelial cell proliferation and G1/S cell-cycle progression, through modulation of pRb/E2F cell-cycle target genes including rrm1. Recently, mutations in THAP1 have been found to cause DYT6 primary torsion dystonia, a human neurological disease. We report here the first 3D structure of the complex formed by the DNA-binding domain of THAP1 and its specific DNA target (THABS) found within the rrm1 target gene. The THAP zinc finger uses its double-stranded β-sheet to fill the DNA major groove and provides a unique combination of contacts from the β-sheet, the N-terminal tail and surrounding loops toward the five invariant base pairs of the THABS sequence. Our studies reveal unprecedented insights into the specific DNA recognition mechanisms within this large family of proteins controlling cell proliferation, cell cycle and pluripotency