Fundamental limits to the measurement of the polarization of classical light

AbstractCombining external control with long spin lifetime and coherence is a key challenge for solid state spin qubits. Tunnel coupling with electron Fermi reservoir provides robust charge state control in semiconductor quantum dots, but results in undesired relaxation of electron and nuclear spins through mechanisms that lack complete understanding. Here, we unravel the contributions of tunnelling-assisted and phonon-assisted spin relaxation mechanisms by systematically adjusting the tunnelling coupling in a wide range, including the limit of an isolated quantum dot. These experiments reveal fundamental limits and trade-offs of quantum dot spin dynamics: while reduced tunnelling can be used to achieve electron spin qubit lifetimes exceeding 1 s, the optical spin initialisation fidelity is reduced below 80%, limited by Auger recombination. Comprehensive understanding of electron-nuclear spin relaxation attained here provides a roadmap for design of the optimal operating conditions in quantum dot spin qubits.

Download Full-text

Fundamental Limits of HRR Profiling and Velocity Compensation for Stepped-Frequency Waveforms

IEEE Transactions on Signal Processing ◽

10.1109/tsp.2014.2337279 ◽

2014 ◽

Vol 62 (17) ◽

pp. 4490-4504 ◽

Cited By ~ 10

Author(s):

Yimin Liu ◽

Tianyao Huang ◽

Huadong Meng ◽

Xiqin Wang

Keyword(s):

Fundamental Limits ◽

Stepped Frequency

Download Full-text

Fundamental limits on the precision of in-memory architectures

Proceedings of the 39th International Conference on Computer-Aided Design ◽

10.1145/3400302.3416344 ◽

2020 ◽

Author(s):

Sujan K. Gonugondla ◽

Charbel Sakr ◽

Hassan Dbouk ◽

Naresh R. Shanbhag

Keyword(s):

Fundamental Limits ◽

Memory Architectures

Download Full-text

Causality, unitarity and symmetry in effective field theory

Journal of High Energy Physics ◽

10.1007/jhep07(2021)143 ◽

2021 ◽

Vol 2021 (7) ◽

Author(s):

Timothy Trott

Keyword(s):

Effective Field ◽

Tree Level ◽

Global Symmetry ◽

Fundamental Limits ◽

Effective Interactions ◽

Effective Contact ◽

Higher Dimensional ◽

Forward Limit ◽

Mass Dimension ◽

Flavour Violation

Abstract Sum rules in effective field theories, predicated upon causality, place restrictions on scattering amplitudes mediated by effective contact interactions. Through unitarity of the S-matrix, these imply that the size of higher dimensional corrections to transition amplitudes between different states is bounded by the strength of their contributions to elastic forward scattering processes. This places fundamental limits on the extent to which hypothetical symmetries can be broken by effective interactions. All analysis is for dimension 8 operators in the forward limit. Included is a thorough derivation of all positivity bounds for a chiral fermion in SU(2) and SU(3) global symmetry representations resembling those of the Standard Model, general bounds on flavour violation, new bounds for interactions between particles of different spin, inclusion of loops of dimension 6 operators and illustration of the resulting strengthening of positivity bounds over tree-level expectations, a catalogue of supersymmetric effective interactions up to mass dimension 8 and 4 legs and the demonstration that supersymmetry unifies the positivity theorems as well as the new bounds.

Download Full-text