109 research outputs found
Distributed quantum sensing in a continuous variable entangled network
Networking plays a ubiquitous role in quantum technology. It is an integral
part of quantum communication and has significant potential for upscaling
quantum computer technologies that are otherwise not scalable. Recently, it was
realized that sensing of multiple spatially distributed parameters may also
benefit from an entangled quantum network. Here we experimentally demonstrate
how sensing of an averaged phase shift among four distributed nodes benefits
from an entangled quantum network. Using a four-mode entangled continuous
variable (CV) state, we demonstrate deterministic quantum phase sensing with a
precision beyond what is attainable with separable probes. The techniques
behind this result can have direct applications in a number of primitives
ranging from biological imaging to quantum networks of atomic clocks
Fiber coupled EPR-state generation using a single temporally multiplexed squeezed light source
A prerequisite for universal quantum computation and other large-scale
quantum information processors is the careful preparation of quantum states in
massive numbers or of massive dimension. For continuous variable approaches to
quantum information processing (QIP), squeezed states are the natural quantum
resources, but most demonstrations have been based on a limited number of
squeezed states due to the experimental complexity in up-scaling. The number of
physical resources can however be significantly reduced by employing the
technique of temporal multiplexing. Here, we demonstrate an application to
continuous variable QIP of temporal multiplexing in fiber: Using just a single
source of squeezed states in combination with active optical switching and a
200 m fiber delay line, we generate fiber-coupled Einstein-Podolsky-Rosen
entangled quantum states. Our demonstration is a critical enabler for the
construction of an in-fiber, all-purpose quantum information processor based on
a single or few squeezed state quantum resources
Deterministic generation of a two-dimensional cluster state
Measurement-based quantum computation offers exponential computational
speed-up via simple measurements on a large entangled cluster state. We propose
and demonstrate a scalable scheme for the generation of photonic cluster states
suitable for universal measurement-based quantum computation. We exploit
temporal multiplexing of squeezed light modes, delay loops, and beam-splitter
transformations to deterministically generate a cylindrical cluster state with
a two-dimensional (2D) topological structure as required for universal quantum
information processing. The generated state consists of more than 30000
entangled modes arranged in a cylindrical lattice with 24 modes on the
circumference, defining the input register, and a length of 1250 modes,
defining the computation depth. Our demonstrated source of 2D cluster states
can be combined with quantum error correction to enable fault-tolerant quantum
computation
Privatisation rescues function following loss of cooperation
A single cheating mutant can lead to the invasion and eventual eradication of cooperation from a population. Consequently, cheat invasion is often considered equal to extinction in empirical and theoretical studies of cooperator-cheat dynamics. But does cheat invasion necessarily equate extinction in nature? By following the social dynamics of iron metabolism in Pseudomonas aeruginosa during cystic fibrosis lung infection, we observed that individuals evolved to replace cooperation with a âprivateâ behaviour. Phenotypic assays showed that cooperative iron acquisition frequently was upregulated early in infection, which, however, increased the risk of cheat invasion. With whole-genome sequencing we showed that if, and only if, cooperative iron acquisition is lost from the population, a private system was upregulated. The benefit of upregulation depended on iron availability. These findings highlight the importance of social dynamics of natural populations and emphasizes the potential impact of past social interaction on the evolution of private traits
Determining thresholds for spatial urban design and transport features that support walking to create healthy and sustainable cities:findings from the IPEN Adult study
An essential characteristic of a healthy and sustainable city is a physically active population. Effective policies for healthy and sustainable cities require evidence-informed quantitative targets. We aimed to identify the minimum thresholds for urban design and transport features associated with two physical activity criteria: at least 80% probability of engaging in any walking for transport and WHO's target of at least 15% relative reduction in insufficient physical activity through walking. The International Physical Activity and the Environment Network Adult (known as IPEN) study (N=11â615; 14 cities across ten countries) provided data on local urban design and transport features linked to walking. Associations of these features with the probability of engaging in any walking for transport and sufficient physical activity (âĽ150 min/week) by walking were estimated, and thresholds associated with the physical activity criteria were determined. Curvilinear associations of population, street intersection, and public transport densities with walking were found. Neighbourhoods exceeding around 5700 people per km(2), 100 intersections per km(2), and 25 public transport stops per km(2) were associated with meeting one or both physical activity criteria. Shorter distances to the nearest park were associated with more physical activity. We use the results to suggest specific target values for each feature as benchmarks for progression towards creating healthy and sustainable cities
- âŚ