Addressing the clumsiness loophole in a Leggett-Garg test of macrorealism

The rise of quantum information theory has lent new relevance to experimental tests for non-classicality, particularly in controversial cases such as adiabatic quantum computing superconducting circuits. The Leggett-Garg inequality is a "Bell inequality in time" designed to indicate whether a single quantum system behaves in a macrorealistic fashion. Unfortunately, a violation of the inequality can only show that the system is either (i) non-macrorealistic or (ii) macrorealistic but subjected to a measurement technique that happens to disturb the system. The "clumsiness" loophole (ii) provides reliable refuge for the stubborn macrorealist, who can invoke it to brand recent experimental and theoretical work on the Leggett-Garg test inconclusive. Here, we present a revised Leggett-Garg protocol that permits one to conclude that a system is either (i) non-macrorealistic or (ii) macrorealistic but with the property that two seemingly non-invasive measurements can somehow collude and strongly disturb the system. By providing an explicit check of the invasiveness of the measurements, the protocol replaces the clumsiness loophole with a significantly smaller "collusion" loophole.Comment: 7 pages, 3 figure

Protecting Quantum Information with Entanglement and Noisy Optical Modes

We incorporate active and passive quantum error-correcting techniques to protect a set of optical information modes of a continuous-variable quantum information system. Our method uses ancilla modes, entangled modes, and gauge modes (modes in a mixed state) to help correct errors on a set of information modes. A linear-optical encoding circuit consisting of offline squeezers, passive optical devices, feedforward control, conditional modulation, and homodyne measurements performs the encoding. The result is that we extend the entanglement-assisted operator stabilizer formalism for discrete variables to continuous-variable quantum information processing.Comment: 7 pages, 1 figur

Quantum Convolutional Coding with Shared Entanglement: General Structure

We present a general theory of entanglement-assisted quantum convolutional coding. The codes have a convolutional or memory structure, they assume that the sender and receiver share noiseless entanglement prior to quantum communication, and they are not restricted to possess the Calderbank-Shor-Steane structure as in previous work. We provide two significant advances for quantum convolutional coding theory. We first show how to "expand" a given set of quantum convolutional generators. This expansion step acts as a preprocessor for a polynomial symplectic Gram-Schmidt orthogonalization procedure that simplifies the commutation relations of the expanded generators to be the same as those of entangled Bell states (ebits) and ancilla qubits. The above two steps produce a set of generators with equivalent error-correcting properties to those of the original generators. We then demonstrate how to perform online encoding and decoding for a stream of information qubits, halves of ebits, and ancilla qubits. The upshot of our theory is that the quantum code designer can engineer quantum convolutional codes with desirable error-correcting properties without having to worry about the commutation relations of these generators.Comment: 23 pages, replaced with final published versio

Patterns of knee osteoarthritis management in general practice:a retrospective cohort study using electronic health records

Objective: This study determined patterns of knee osteoarthritis (OA) management by general practitioners (GPs) using routine healthcare data from Dutch general practices from 2011 to 2019. Design: A retrospective cohort study was conducted using the Integrated Primary Care Information database between 2011 and 2019. Electronic health records (EHRs) of n = 750 randomly selected knee OA patients (with either codified or narrative diagnosis) were reviewed against eligibility criteria and n = 503 patients were included. Recorded information was extracted on GPs’ management from six months before to three years after diagnosis and patterns of management were analysed.Results: An X-ray referral was the most widely recorded management modality (63.2%). The next most widely recorded management modalities were a referral to secondary care (56.1%) and medication prescription or advice (48.3%). Records of recommendation of/referral to other primary care practitioners (e.g. physiotherapists) were found in only one third of the patients. Advice to lose weight was least common (1.2%). Records of medication prescriptions or recommendation of/referral to other primary care practitioners were found more frequently in patients with an X-ray referral compared to patients without, while records of secondary care referrals were found less frequently. Records of an X-ray referral were often found in narratively diagnosed knee OA patients before GPs recorded a code for knee OA in their EHR. Conclusion: These findings emphasize the importance of better implementing non-surgical management of knee OA in general practice and on initiatives for reducing the overuse of X-rays for diagnosing knee OA in general practice.</p

The intrinsic features of the specific heat at half-filled Landau levels of two-dimensional electron systems

The specific heat capacity of a two-dimensional electron gas is derived for two types of the density of states, namely, the Dirac delta function spectrum and that based on a Gaussian function. For the first time, a closed form expression of the specific heat for each case is obtained at half-filling. When the chemical potential is temperature-independent, the temperature is calculated at which the specific heat is a maximum. Here the effects of the broadening of the Landau levels are distinguished from those of the different filling factors. In general, the results derived herein hold for any thermodynamic system having similar resonant states.Comment: 11 pages, 1 figure, to appear in J Low Temp Phys (2010

Antidepressant and anticonvulsant prescription rates in patients with osteoarthritis:A population-based cohort study

Objectives: There are signs that antidepressants and anticonvulsants are being prescribed more often for OA patients, despite limited evidence. Our objectives were to examine prescription rates and time trends for antidepressants and anticonvulsants in OA patients, to assess the percentage of long-term prescriptions, and to determine patient characteristics associated with antidepressant or anticonvulsant prescription. Methods: A population-based cohort study was conducted using the Integrated Primary Care Information database. First, episodic and prevalent prescription rates for antidepressants (amitriptyline, nortriptyline and duloxetine) and anticonvulsants (gabapentinoids) in OA patients were calculated for the period 2008-17. Logistic regression was used to assess which patient characteristics were associated with prescriptions.  Results: In total, 164 292 OA patients were included. The prescription rates of amitriptyline, gabapentin and pregabalin increased over time. The increase in prescription rates for pregabalin was most pronounced. Episodic prescription rate increased from 7.1 to 13.9 per 1000 person-years between 2008 and 2017. Amitriptyline was prescribed most (15.1 episodic prescriptions per 1000 person-years in 2017). Prescription rates of nortriptyline and duloxetine remained stable at 3.0 and 2.0 episodic prescriptions per 1000 person-years, respectively. For ≤3% of patients with incident OA, medication was prescribed long-term (≥3 months). In general, all medication was prescribed more frequently for older patients (except duloxetine), women, patients with OA in ≥2 joints, patients with spinal OA and patients with musculoskeletal disorders.  Conclusion: Prescription rates of amitriptyline, gabapentin and pregabalin increased over time. Since there is little evidence to support prescription in OA, caution is necessary when prescribing. </p

Persistent spin splitting of a two-dimensional electron gas in tilted magnetic fields

By varying the orientation of the applied magnetic field with respect to the normal of a two-dimensional electron gas, the chemical potential and the specific heat reveal persistent spin splitting in all field ranges. The corresponding shape of the thermodynamic quantities distinguishes whether the Rashba spin-orbit interaction RSOI, the Zeeman term or both dominate the splitting. The interplay of the tilting of the magnetic field and RSOI resulted to an amplified splitting in weak fields. The effects of changing the RSOI strength and the Landau level broadening are also investigated.Comment: 10 pages, 5 figure

The quantum dynamic capacity formula of a quantum channel

The dynamic capacity theorem characterizes the reliable communication rates of a quantum channel when combined with the noiseless resources of classical communication, quantum communication, and entanglement. In prior work, we proved the converse part of this theorem by making contact with many previous results in the quantum Shannon theory literature. In this work, we prove the theorem with an "ab initio" approach, using only the most basic tools in the quantum information theorist's toolkit: the Alicki-Fannes' inequality, the chain rule for quantum mutual information, elementary properties of quantum entropy, and the quantum data processing inequality. The result is a simplified proof of the theorem that should be more accessible to those unfamiliar with the quantum Shannon theory literature. We also demonstrate that the "quantum dynamic capacity formula" characterizes the Pareto optimal trade-off surface for the full dynamic capacity region. Additivity of this formula simplifies the computation of the trade-off surface, and we prove that its additivity holds for the quantum Hadamard channels and the quantum erasure channel. We then determine exact expressions for and plot the dynamic capacity region of the quantum dephasing channel, an example from the Hadamard class, and the quantum erasure channel.Comment: 24 pages, 3 figures; v2 has improved structure and minor corrections; v3 has correction regarding the optimizatio

Perfect state distinguishability and computational speedups with postselected closed timelike curves

Bennett and Schumacher's postselected quantum teleportation is a model of closed timelike curves (CTCs) that leads to results physically different from Deutsch's model. We show that even a single qubit passing through a postselected CTC (P-CTC) is sufficient to do any postselected quantum measurement, and we discuss an important difference between "Deutschian" CTCs (D-CTCs) and P-CTCs in which the future existence of a P-CTC might affect the present outcome of an experiment. Then, based on a suggestion of Bennett and Smith, we explicitly show how a party assisted by P-CTCs can distinguish a set of linearly independent quantum states, and we prove that it is not possible for such a party to distinguish a set of linearly dependent states. The power of P-CTCs is thus weaker than that of D-CTCs because the Holevo bound still applies to circuits using them regardless of their ability to conspire in violating the uncertainty principle. We then discuss how different notions of a quantum mixture that are indistinguishable in linear quantum mechanics lead to dramatically differing conclusions in a nonlinear quantum mechanics involving P-CTCs. Finally, we give explicit circuit constructions that can efficiently factor integers, efficiently solve any decision problem in the intersection of NP and coNP, and probabilistically solve any decision problem in NP. These circuits accomplish these tasks with just one qubit traveling back in time, and they exploit the ability of postselected closed timelike curves to create grandfather paradoxes for invalid answers.Comment: 15 pages, 4 figures; Foundations of Physics (2011

Over de relatie tussen rekenmodellen de beleidscontext en de visserijpraktijk: LNV Bestek Ond/2002-1/6C/01 Verbetering rekenmodel voor visquota

LNV Bestek Ond/2002-1/6C/01 Verbeteringrekenmodel voor visquota beoogt de zekerstelling van de technische en politieke bruikbaarheid van het gekozen rekenmodel voor de bepaling van TACs en quota in het Gemeenschappelijk Visserij Beleid. Het tweejarig onderzoekprogramma (2002/2003) is geformuleerd naar aanleiding van een aantal kennisvragen bij de Directie Vis van LNV met betrekking tot de onderbouwing van aan het rekenmodel ten grondslag liggende aannames, effecten van onzekerheden in parameterschattingen, mogelijke verbeteringen en alternatieve beleidsopties. Hiertoe zijn de kennisvragen vertaald in een viertal onderzoeksvragen, waarover afzonderlijk gerapporteerd zal worden. Dit rapport (product 2) heeft betrekking op onderzoeksvraag 2, ‘Wat is de relatie tussen de rekenmodellen en de beleidscontext en visserijpraktijk en hoe worden zij wederzijds beïnvloed?’ en dient als achtergronddocument voor de meer specifieke vragen die in de overige deelonderzoeken aan de orde zullen komen