Efficient photon sorter in a high-dimensional state space

2011 ◽  
Vol 11 (3&4) ◽  
pp. 313-325
Author(s):  
Warner A. Miller
Keyword(s):  
Quantum Information ◽  
State Space ◽  
Quantum Key Distribution ◽  
Quantum Information Processing ◽  
Three Dimensional ◽  
High Dimensional ◽  
Coupled Mode Theory ◽  
Coupled Mode ◽  
Dimensional State Space ◽  
Significant Obstacle

An increase in the dimension of state space for quantum key distribution (QKD) can decrease its fidelity requirements while also increasing its bandwidth. A significant obstacle for QKD with qu$d$its ($d\geq 3$) has been an efficient and practical quantum state sorter for photons whose complex fields are modulated in both amplitude and phase. We propose such a sorter based on a multiplexed thick hologram, constructed e.g. from photo-thermal refractive (PTR) glass. We validate this approach using coupled-mode theory with parameters consistent with PTR glass to simulate a holographic sorter. The model assumes a three-dimensional state space spanned by three tilted planewaves. The utility of such a sorter for broader quantum information processing applications can be substantial.

scholarly journals Bogoliubov quasiparticles in superconducting qubits

2021 ◽  
Author(s):  
Leonid Glazman ◽  
Gianluigi Catelani
Keyword(s):  
Information Processing ◽  
Quantum Information ◽  
Adverse Effects ◽  
Quantum Information Processing ◽  
Photon Emission ◽  
Three Dimensional ◽  
Degree Of Freedom ◽  
Superconducting Qubits ◽  
Relaxation Rates ◽  
Circuit Qed

Extending the qubit coherence times is a crucial task in building quantum information processing devices. In the three-dimensional cavity implementations of circuit QED, the coherence of superconducting qubits was improved dramatically due to cutting the losses associated with the photon emission. Next frontier in improving the coherence includes the mitigation of the adverse effects of superconducting quasiparticles. In these lectures, we review the basics of the quasiparticles dynamics, their interaction with the qubit degree of freedom, their contribution to the qubit relaxation rates, and approaches to control their effect.

Thermal geometric discords in a two-qutrit system

2016 ◽  
Vol 14 (03) ◽  
pp. 1650016 ◽  
Author(s):  
Ya-Li Yuan ◽  
Xi-Wen Hou
Keyword(s):  
Magnetic Field ◽  
Quantum Information ◽  
Magnetic Fields ◽  
Weak Magnetic Field ◽  
Quantum Discord ◽  
Quantum Information Processing ◽  
Thermal State ◽  
Quantum Correlations ◽  
High Dimensional ◽  
Lower Temperature

The investigation of quantum discord has mostly focused on two-qubit systems due to the complicated minimization involved in quantum discord for high-dimensional states. In this work, three geometric discords are studied for the thermal state in a two-qutrit system with various couplings, external magnetic fields, and temperatures as well, where the entanglement measured in terms of the generalized negativity is calculated for reference. It is shown that three geometric discords are more robust against temperature and magnetic field than the entanglement negativity. However, all four quantities exhibit a similar behavior at lower temperature and weak magnetic field. Remarkably, three geometric discords at finite temperature reveal the phenomenon of double sudden changes at different magnetic fields while the negativity does not. Moreover, the hierarchy among three discords is discussed. Those adjustable discords with the varied coupling, temperature, and magnetic field are useful for the understanding of quantum correlations in high-dimensional states and quantum information processing.

scholarly journals Bounding on rough terrain with the LittleDog robot

2010 ◽  
Vol 30 (2) ◽  
pp. 192-215 ◽  
Author(s):  
Alexander Shkolnik ◽  
Michael Levashov ◽  
Ian R. Manchester ◽  
Russ Tedrake
Keyword(s):  
State Space ◽  
Open Loop ◽  
Random Trees ◽  
Configuration Spaces ◽  
High Dimensional ◽  
Rough Terrain ◽  
Task Space ◽  
Motion Primitive ◽  
Dimensional State Space ◽  
Planning Algorithm

A motion planning algorithm is described for bounding over rough terrain with the LittleDog robot. Unlike walking gaits, bounding is highly dynamic and cannot be planned with quasi-steady approximations. LittleDog is modeled as a planar five-link system, with a 16-dimensional state space; computing a plan over rough terrain in this high-dimensional state space that respects the kinodynamic constraints due to underactuation and motor limits is extremely challenging. Rapidly Exploring Random Trees (RRTs) are known for fast kinematic path planning in high-dimensional configuration spaces in the presence of obstacles, but search efficiency degrades rapidly with the addition of challenging dynamics. A computationally tractable planner for bounding was developed by modifying the RRT algorithm by using: (1) motion primitives to reduce the dimensionality of the problem; (2) Reachability Guidance, which dynamically changes the sampling distribution and distance metric to address differential constraints and discontinuous motion primitive dynamics; and (3) sampling with a Voronoi bias in a lower-dimensional “task space” for bounding. Short trajectories were demonstrated to work on the robot, however open-loop bounding is inherently unstable. A feedback controller based on transverse linearization was implemented, and shown in simulation to stabilize perturbations in the presence of noise and time delays.

Quantum non-gaussianity from an indefnite causal order of Gaussian operations

2021 ◽  
Author(s):  
Seid Koudia ◽  
Abdelhakim Gharbi
Keyword(s):  
Quantum Information ◽  
Quantum Key Distribution ◽  
Degrees Of Freedom ◽  
Quantum Communication ◽  
Quantum Information Processing ◽  
Quantum Metrology ◽  
Causal Order ◽  
Gaussian States ◽  
Control Qubit ◽  
Non Gaussian

Quantum non-Gaussian states are considered a useful resource for many tasks in quantum information processing, from quantum metrology and quantum sensing to quantum communication and quantum key distribution. Another useful tool that is gaining attention is the newly constructed quantum switch. Its applications in many tasks in quantum information have been proved to outperform many existing schemes in quantum communication and quantum thermometry. In this contribution, we demonstrate this to be very useful for engineering highly non-Gaussian states from Gaussian operations whose order is controlled by degrees of freedom of a control qubit. The nonconvexity of the set of Gaussian states and the set of Gaussian operations guarantees the emergence of non-Gaussianity after post-selection on the control qubit deterministically, in contrast to existing protocols in the literature. The nonclassicality of the resulting states is discussed accordingly.

Pay no attention to that man behind the curtain

2016 ◽  
Vol 11 (3) ◽  
pp. 350-374 ◽  
Author(s):  
Chris Westbury
Keyword(s):  
Associative Learning ◽  
State Space ◽  
Neural Activity ◽  
Scientific Explanation ◽  
Word Meaning ◽  
Mental Simulation ◽  
High Dimensional ◽  
Weighted Constraints ◽  
Dimensional State Space ◽  
Semantic Domains

There is a distinction in scientific explanation between the explanandum, statements describing the empirical phenomenon to be explained, and the explanans, statements describing the evidence that allow one to predict that phenomenon. To avoid tautology, these sets of statements must refer to distinct domains. A scientific explanation of semantics must be grounded in explanans that appeal to entities from non-semantic domains. I consider as examples eight candidate domains (including affect, lexical or sub-word co-occurrence, mental simulation, and associative learning) that could ground semantics. Following Wittgenstein (1954), I propose adjudicating between these different domains is difficult because of the reification of a word’s ‘meaning’ as an atomistic unit. If we abandon the idea of the meaning of a word as being an atomistic unit and instead think of word meaning as a set of dynamic and disparate embodied states unified by a shared label, many apparent problems associated with identifying a meaning’s ‘true’ explanans disappear. Semantics can be considered as sets of weighted constraints that are individually sufficient for specifying and labeling a subjectively-recognizable location in the high dimensional state space defined by our neural activity.

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