Generation of mechanical interference fringes by multi-photon counting

Exploring the quantum behaviour of macroscopic objects provides an intriguing avenue to study the foundations of physics and to develop a suite of quantum-enhanced technologies. One prominent path of study is provided by quantum optomechanics which utilizes the tools of quantum optics to control the motion of macroscopic mechanical resonators. Despite excellent recent progress, the preparation of mechanical quantum superposition states remains outstanding due to weak coupling and thermal decoherence. Here we present a novel optomechanical scheme that significantly relaxes these requirements allowing the preparation of quantum superposition states of motion of a mechanical resonator by exploiting the nonlinearity of multi-photon quantum measurements. Our method is capable of generating non-classical mechanical states without the need for strong single photon coupling, is resilient against optical loss, and offers more favourable scaling against initial mechanical thermal occupation than existing schemes. Moreover, our approach allows the generation of larger superposition states by projecting the optical field onto NOON states. We experimentally demonstrate this multi-photon-counting technique on a mechanical thermal state in the classical limit and observe interference fringes in the mechanical position distribution that show phase superresolution. This opens a feasible route to explore and exploit quantum phenomena at a macroscopic scale.Comment: 16 pages, 4 figures. v1: submitted for review on 28 Jan 2016. v2: significantly revised manuscript. v3: some further revisions and some extra results included. v3: new results added, extra author added, close to published version, supplementary material available with published versio

Quantum and Classical Phases in Optomechanics

The control of quantum systems requires the ability to change and read-out the phase of a system. The non-commutativity of canonical conjugate operators can induce phases on quantum systems, which can be employed for implementing phase gates and for precision measurements. Here we study the phase acquired by a radiation field after its radiation pressure interaction with a mechanical oscillator, and compare the classical and quantum contributions. The classical description can reproduce the nonlinearity induced by the mechanical oscillator and the loss of correlations between mechanics and optical field at certain interaction times. Such features alone are therefore insufficient for probing the quantum nature of the interaction. Our results thus isolate genuine quantum contributions of the optomechanical interaction that could be probed in current experiments.Comment: 10 pages, 3 figure

Non-linear optomechanical measurement of mechanical motion

Precision measurement of non-linear observables is an important goal in all facets of quantum optics. This allows measurement-based non-classical state preparation, which has been applied to great success in various physical systems, and provides a route for quantum information processing with otherwise linear interactions. In cavity optomechanics much progress has been made using linear interactions and measurement, but observation of non-linear mechanical degrees-of-freedom remains outstanding. Here we report the observation of displacement-squared thermal motion of a micro-mechanical resonator by exploiting the intrinsic non-linearity of the radiation pressure interaction. Using this measurement we generate bimodal mechanical states of motion with separations and feature sizes well below 100~pm. Future improvements to this approach will allow the preparation of quantum superposition states, which can be used to experimentally explore collapse models of the wavefunction and the potential for mechanical-resonator-based quantum information and metrology applications.Comment: 8 pages, 4 figures, extensive supplementary material available with published versio

Researchers Experience Multiple Embodiments in a Cross-Cultural, Intergenerational Event to Support Girls Challenging Gender-Based Violence

Many challenges exist to conducting participatory research and consultation with young people, especially with those considered vulnerable or at risk. Beyond respecting the safety and wellbeing of young research participants, researchers must be aware of barriers to youth engagement and be attuned to the many forms of youth resistance. As young people are seeking more control over their lives, traditional knowledge hierarchies between adults and youth are shifting. In July 2018, an event entitled Circles Within Circles brought together Indigenous and non-Indigenous girls and young women from South Africa, Canada, Russia, Sweden, and Kenya to learn from each other’s participatory art-making and create a network for challenging gender-based violence (GBV). This article provides insight into the often-invisible experience of the “supporting cast” in events like Circles Within Circles. The co-authors are doctoral and postdoctoral researchers who contributed to organization and acted as facilitators, notetakers, and participants. The co-authors conduct participatory analyses of journal entries they wrote throughout the event, and jointly reflect on the activities and their feelings about their roles. Reflecting, for example, on gut feelings about young participants’ use of voice and silence during adult-led activities, the co-authors discuss their reading of girls’ demonstrations of resistance. This embodied knowledge, further cultivated by attuning to shared experience, is explored in this collaborative auto-ethnography. Examining the complexities of this cross-cultural and intergenerational event, the co-authors contend that when supporting girls and young people subverting dominant narratives of GBV, researchers’ embodied reflexivity is crucial for positively contributing to girl-led change

Quantum Hypercube States

We introduce quantum hypercube states, a class of continuous-variable quantum states that are generated as orthographic projections of hypercubes onto the quadrature phase-space of a bosonic mode. In addition to their interesting geometry, hypercube states display phase-space features much smaller than Planck's constant, and a large volume of Wigner-negativity. We theoretically show that these features make hypercube states sensitive to displacements at extremely small scales in a way that is surprisingly robust to initial thermal occupation and to small separation of the superposed state-components. In a high-temperature proof-of-principle optomechanics experiment we observe, and match to theory, the signature outer-edge vertex structure of hypercube states.Comment: Main consists of 5 pages and 5 figures. Supplementary material consists of 5 pages and 6 figure

Scoping study to identify potential circular economy actions, priority sectors, material flows and value chains

The circular economy is rapidly rising up political and business agendas. In contrast to today’s largely linear, ‘take-make-use-dispose’ economy, a circular economy represents a development strategy that enables economic growth while aiming to optimise the chain of consumption of biological and technical materials. A deep transformation of production chains and consumption patterns is envisaged to keep materials circulating in the economy for longer, re-designing industrial systems and encouraging cascading use of materials and waste. Although there are some elements of circularity such as recycling and composting in the linear economy (see Figure E1) where progress needs to be maintained, a circular economy goes beyond the pursuit of waste prevention and waste reduction to inspire technological, organisational and social innovation across and within value chains (see Figure E2). There are already several policies in place and activities underway that support a circular economy; however there remain a range of untapped opportunities, costs to be avoided and obstacles to be addressed in order to accelerate the move towards a circular economy in the EU. Against this backdrop, the European Commission (DG Environment) launched a Scoping study to identify potential circular economy actions, priority sectors, material flows & value chains. The study was carried out by the Policy Studies Institute (PSI), Institute for European Environmental Policy (IEEP), BIO and Ecologic Institute between November 2013 and July 2014. The aim of the study was to provide an initial scoping assessment of potential priorities and policy options to support the transition to a circular economy in the EU. The study reviewed existing literature, identified potential priority areas for action where accelerating the circular economy would be beneficial and where EU policy has a particular role to play, and developed policy options for consideration across a range of areas

Pulsed quantum optomechanics

Studying mechanical resonators via radiation pressure offers a rich avenue for the exploration of quantum mechanical behavior in a macroscopic regime. However, quantum state preparation and especially quantum state reconstruction of mechanical oscillators remains a significant challenge. Here we propose a scheme to realize quantum state tomography, squeezing and state purification of a mechanical resonator using short optical pulses. The scheme presented allows observation of mechanical quantum features despite preparation from a thermal state and is shown to be experimentally feasible using optical microcavities. Our framework thus provides a promising means to explore the quantum nature of massive mechanical oscillators and can be applied to other systems such as trapped ions.Comment: 9 pages, 4 figure