Swarm optimization for adaptive phase measurements with low visibility

Adaptive feedback normally provides the greatest accuracy for optical phase measurements. New advances in nitrogen vacancy centre technology have enabled magnetometry via individual spin measurements, which are similar to optical phase measurements but with low visibility. The adaptive measurements that previously worked well with high-visibility optical interferometry break down and give poor results for nitrogen vacancy centre measurements. We use advanced search techniques based on swarm optimisation to design better adaptive measurements that can provide improved measurement accuracy with low-visibility interferometry, with applications in nitrogen vacancy centre magnetometry.Comment: 8 pages, 7 figures, comments welcom

Sammelbesprechung

Joan Steigerwald 2019: Experimenting at the Boundaries of Life: Organic Vitality in Germany around 1800 . Pittsburgh: University of Pittsburgh Press, geb., ix+ 460 S., 55.00 US$, ISBN: 9780822945536. Andrew Reynolds 2018: The Third Lens. Metaphor and the Creation of Modern Cell Biology . Chicago: University of Chicago Press, brosch., 272 S., 17 Abb., 30.00 US$, ISBN: 9780226563268. Mathias Grote (2019): Membranes to Molecular Machines: Active Matter and the Remaking of Life . Chicago: University of Chicago Press, geb., 296 S., 27 Abb., 45 US$. ISBN: 9780226625157

Making DNA and its becoming an experimental commodity

This paper pursues the history of biology and technology in tandem. It focuses on DNA’s materiality regardless of informational properties. My emphasis on ‘making’ integrates attention to cultures of work in material histories of biology with analyses of the development of technical apparatuses and machines. When it comes to the history of DNA synthesis our materials are as much chemical as they are biological, which means that there is really a third history present, one that also needs to be drawn in, but on its own terms. I demonstrate the ways in which different chemistries have been combined with different technologies, all together affording different arrangements of personnel and biological science. It is a history of how synthesised DNA first came to be, became desired, and became a commodity, available for inclusion in a wide variety of experiments and experimental systems. This method could be replicated for other ‘experimental commodities’

Stochastic Heisenberg limit: Optimal estimation of a fluctuating phase

The ultimate limits to estimating a fluctuating phase imposed on an optical beam can be found using the recently derived continuous quantum Cramer-Rao bound. For Gaussian stationary statistics, and a phase spectrum scaling asymptotically as 1/omega^p with p>1, the minimum mean-square error in any (single-time) phase estimate scales as N^{-2(p-1)/(p+1)}, where N is the photon flux. This gives the usual Heisenberg limit for a constant phase (as the limit p--> infinity) and provides a stochastic Heisenberg limit for fluctuating phases. For p=2 (Brownian motion), this limit can be attained by phase tracking.Comment: 5+4 pages, to appear in Physical Review Letter

The quantum Bell-Ziv-Zakai bounds and Heisenberg limits for waveform estimation

We propose quantum versions of the Bell-Ziv-Zakai lower bounds on the error in multiparameter estimation. As an application we consider measurement of a time-varying optical phase signal with stationary Gaussian prior statistics and a power law spectrum $\sim 1/|\omega|^p$, with $p>1$. With no other assumptions, we show that the mean-square error has a lower bound scaling as $1/{\cal N}^{2(p-1)/(p+1)}$, where ${\cal N}$ is the time-averaged mean photon flux. Moreover, we show that this accuracy is achievable by sampling and interpolation, for any $p>1$. This bound is thus a rigorous generalization of the Heisenberg limit, for measurement of a single unknown optical phase, to a stochastically varying optical phase.Comment: 18 pages, 6 figures, comments welcom

Optimal Heisenberg-style bounds for the average performance of arbitrary phase estimates

The ultimate bound to the accuracy of phase estimates is often assumed to be given by the Heisenberg limit. Recent work seemed to indicate that this bound can be violated, yielding measurements with much higher accuracy than was previously expected. The Heisenberg limit can be restored as a rigorous bound to the accuracy provided one considers the accuracy averaged over the possible values of the unknown phase, as we have recently shown [Phys. Rev. A 85, 041802(R) (2012)]. Here we present an expanded proof of this result together with a number of additional results, including the proof of a previously conjectured stronger bound in the asymptotic limit. Other measures of the accuracy are examined, as well as other restrictions on the generator of the phase shifts. We provide expanded numerical results for the minimum error and asymptotic expansions. The significance of the results claiming violation of the Heisenberg limit is assessed, followed by a detailed discussion of the limitations of the Cramer-Rao bound.Comment: 22 pages, 4 figure

Experimental optical phase measurement approaching the exact Heisenberg limit

The use of quantum resources can provide measurement precision beyond the shot-noise limit (SNL). The task of ab initio optical phase measurement---the estimation of a completely unknown phase---has been experimentally demonstrated with precision beyond the SNL, and even scaling like the ultimate bound, the Heisenberg limit (HL), but with an overhead factor. However, existing approaches have not been able---even in principle---to achieve the best possible precision, saturating the HL exactly. Here we demonstrate a scheme to achieve true HL phase measurement, using a combination of three techniques: entanglement, multiple samplings of the phase shift, and adaptive measurement. Our experimental demonstration of the scheme uses two photonic qubits, one double passed, so that, for a successful coincidence detection, the number of photon-passes is $N=3$. We achieve a precision that is within $4\%$ of the HL, surpassing the best precision theoretically achievable with simpler techniques with $N=3$. This work represents a fundamental achievement of the ultimate limits of metrology, and the scheme can be extended to higher $N$ and other physical systems.Comment: (12 pages, 6 figures), typos correcte

Synthesis and the organism: biology, chemistry, and engineering

This workshop attended to the ways in which methods for the chemical synthesis of organic materials has mattered, and continues to matter, for biological science and technology. It adopted a fundamentally historical approach with a focus on the synthesis of DNA, and was informed by accounts from scientific practitioners, social scientists, museologists, philosophers, and historians. The workshop’s investigation was inspired by a focal point: the efforts of a small international community of scientists and engineers who from around the 1960s picked up the challenge of synthesizing nucleotide sequences without having to rely on finding desired sequences in existing organisms. This was the making of sequences through chemistry, technology and engineering. While the historiography of biotechnology is vast, the capacity for DNA synthesis itself has largely gone unnoticed, the vast majority of work focusing on techniques for recombination, its meanings, broader social significance, and reception amongst diverse publics. By staying focussed on the particularities of biological molecules as synthesised the workshop aimed to break new ground, drawing in material culture, engineering studies, and their historical, philosophical and sociological intersections. While DNA synthesis was the focal point, these activities needed to be understood in a longer and broader context, right up to the present. Speakers accordingly focussed on a range of periods, and highlighted different features when it came to synthesis and the organism, each with an emphasis on different kinds of scientific, commercial, or organic actor. Indeed it is no doubt thanks to the diversity of the kinds of actor involved that scholars in the history of science have yet to grapple with the cases addressed here, the majority staying within either chemistry, biology, or engineering. This workshop recognises that synthesis sits in an uncomfortable research space for historians and philosophers of science. It was dedicated to addressing this discomfort and producing materials for the systematic international investigation of nonbiological, or perhaps ‘mechano-chemical’ DNA synthesis, the philosophical questions it provokes, the historiographical revisionism it invites, and the social relations it changes. Part 1 of the report incorporates short summaries of the papers given (each of which was 20 minutes in length) and reports of the question period. Part 2 includes the biographies of our participants. In an annex we include copies of the workshop documentation