| 1. |
- Jönsen, Andreas, et al.
(författare)
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Direct and indirect costs for systemic lupus erythematosus in Sweden. A nationwide health economic study based on five defined cohorts
- 2016
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Ingår i: Seminars in Arthritis & Rheumatism. - : Elsevier BV. - 0049-0172 .- 1532-866X. ; 45:6, s. 684-690
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Forskningsöversikt (refereegranskat)abstract
- Objectives: The main objectives of this study were to calculate total costs of illness and cost -driving disease features among patients with systemic lupus erythematosus (SLE) in Sweden. Methods: Five cohorts of well-defined SLE patients, located in different parts of the country were merged. Incident and prevalent cases from 2003 through 2010 were included. The American College of Rheumatology (ACR) classification criteria was used. From the local cohorts, data on demographics, disease activity (SLEDAI 2K), and organ damage (SDI) were collected. Costs for inpatient care, specialist outpatient care and drugs were retrieved from national registries at the National Board of Health and Welfare. Indirect costs were calculated based on sickness leave and disability pensions from the Swedish Social Insurance Agency. Results: In total, 1029 SLE patients, 88% females, were included, and approximately 75% were below 65 years at the end of follow-up, and thus in working age. The mean number of annual specialist physician visits varied from six to seven; mean annual inpatient days were 3.1-3.6, and mean annual sick leave was 123-148 days, all per patient. The total annual cost was 208,555 SEK ($33,369 = 22,941(sic)), of which direct cost was 63,672kr ($10,188 = 7004(sic)) and the indirect cost was 144,883 SEK ($23,181 = 15,937(sic)), all per patient. The costs for patients with short disease duration were higher. Higher disease activity as measured by a SLEDAI 2K score > 3 was associated with approximately 50% increase in both indirect and direct costs. Damage in the neuropsychiatric and musculoskeletal domains were also linked to higher direct and indirect costs, while organ damage in the renal and ocular systems increased direct costs. Conclusion: Based on this study and an estimate of slightly more than 6000 SLE patients in Sweden, the total annual cost for SLE in the country is estimated at $188 million (= 129.5 million (sic)). Both direct (30%) and indirect costs (70%) are substantial. Medication accounts for less than 10% of the total cost. The tax paid national systems for health care and social security in Sweden ensure equal access to health care, sick leave reimbursements, and disability pensions nationwide. Our extrapolated annual costs for SLE in Sweden are therefore the best supported estimations thus far, and they clearly underline the importance of improved management, especially to reduce the indirect costs. (C) 2016 Elsevier Inc. All rights reserved.
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| 2. |
- Andersson, David, et al.
(författare)
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States that are far from being stabilizer states
- 2015
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Ingår i: Journal of Physics A. - : IOP Publishing. - 1751-8113 .- 1751-8121. ; 48:34
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Tidskriftsartikel (refereegranskat)abstract
- Stabilizer states are eigenvectors of maximal commuting sets of operators in a finite Heisenberg group. States that are far from being stabilizer states include magic states in quantum computation, MUB-balanced states, and SIC vectors. In prime dimensions the latter two fall under the umbrella of minimum uncertainty states (MUSs) in the sense of Wootters and Sussman. We study the correlation between two ways in which the notion of ` far from being a stabilizer state' can be quantified. Two theorems valid for all prime dimensions are given, as well as detailed results for low dimensions. In dimension 7 we identify the MUB-balanced states as being antipodal to the SIC vectors within the set of MUS, in a sense that we make definite. In dimension 4 we show that the states that come closest to being MUS with respect to all of the six stabilizer MUBs are the fiducial vectors for Alltop MUBs.
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| 3. |
- Andersson, Ole, et al.
(författare)
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Clifford tori and unbiased vectors
- 2017
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Ingår i: Reports on mathematical physics. - : Elsevier. - 0034-4877 .- 1879-0674. ; 79:1, s. 33-51
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Tidskriftsartikel (refereegranskat)abstract
- The existence problem for mutually unbiased bases is an unsolved problem in quantum information theory. A related question is whether every pair of bases admits vectors that are unbiased to both. Mathematically this translates to the question whether two Lagrangian Clifford tori intersect, and a body of results exists concerning it. These results are however rather weak from the point of view of the first problem. We make a detailed study of how the intersections behave in the simplest nontrivial case, that of complex projective 2-space (the qutrit), for which the set of pairs of Clifford tori can be usefully parametrized by the unistochastic subset of Birkhoff's polytope. Pairs that do not intersect transversally are located. Some calculations in higher dimensions are included to see which results are special to the qutrit.
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| 4. |
- Andersson, Ole, et al.
(författare)
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Geometric phases for mixed states of the Kitaev chain
- 2016
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Ingår i: Philosophical Transactions. Series A. - : The Royal Society. - 1364-503X .- 1471-2962. ; 374:2069
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Tidskriftsartikel (refereegranskat)abstract
- The Berry phase has found applications in building topological order parameters for certain condensed matter systems. The question whether some geometric phase for mixed states can serve the same purpose has been raised, and proposals are on the table. We analyze the intricate behaviour of Uhlmann’s geometric phase in the Kitaev chain at finite temperature, and then argue that it captures quite different physics from that intended. We also analyze the behaviour of a geometric phase introduced in the context of interferometry. For the Kitaev chain, this phase closely mirrors that of the Berry phase, and we argue that it merits further investigation.
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| 5. |
- Andersson, Ole
(författare)
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Holonomy in Quantum Information Geometry
- 2018
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis we provide a uniform treatment of the two most popular non-adiabatic geometric phases for dynamical systems of mixed quantum states, namely those of Uhlmann and of Sjöqvist et al. We develop a holonomy theory for the latter which we also relate to the already existing theory for the former. This makes it clear what the similarities and differences between the two geometric phases are. We discuss and motivate constraints on the two phases. Furthermore, we discuss some topological properties of the holonomy of `real' quantum systems, and we introduce higher-order geometric phases for not necessarily cyclic dynamical systems of mixed states. In a final chapter we apply the theory developed for the geometric phase of Sjöqvist et al. to geometric uncertainty relations, including some new "quantum speed limits''.
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| 6. |
- Andersson, Ole, et al.
(författare)
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Self-testing properties of Gisin's elegant Bell inequality
- 2017
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Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - : American Physical Society. - 2469-9926 .- 2469-9934. ; 96:3
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Tidskriftsartikel (refereegranskat)abstract
- An experiment in which the Clauser-Horne-Shimony-Holt inequality is maximally violated is self-testing (i.e., it certifies in a device-independent way both the state and the measurements). We prove that an experiment maximally violating Gisin's elegant Bell inequality is not similarly self-testing. The reason can be traced back to the problem of distinguishing an operator from its complex conjugate. We provide a complete and explicit characterization of all scenarios in which the elegant Bell inequality is maximally violated. This enables us to see exactly how the problem plays out.
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| 7. |
- Appleby, D. M., et al.
(författare)
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GALOIS UNITARIES, MUTUALLY UNBIASED BASES, AND MUB-BALANCED STATES
- 2015
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Ingår i: Quantum information & computation. - 1533-7146. ; 15:15-16, s. 1261-1294
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Tidskriftsartikel (refereegranskat)abstract
- A Galois unitary is a generalization of the notion of anti-unitary operators. They act only on those vectors in Hilbert space whose entries belong to some chosen number field. For Mutually Unbiased Bases the relevant number field is a cyclotomic field. By including Galois unitaries we are able to remove a mismatch between the finite projective group acting on the bases on the one hand, and the set of those permutations of the bases that can be implemented as transformations in Hilbert space on the other hand. In particular we show that there exist transformations that cycle through all the bases in all dimensions d - p(n) where p is an odd prime and the exponent n is odd. (For even primes unitary MUB-cyclers exist.) These transformations have eigenvectors, which are MUB-balanced states (i.e. rotationally symmetric states in the original terminology of Wootters and Sussman) if and only if d = 3 modulo 4. We conjecture that this construction yields all such states in odd prime power dimension.
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| 8. |
- Appleby, D.M., et al.
(författare)
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Systems of Imprimitivity for the Clifford Group
- 2014
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Ingår i: Quantum information & computation. - : Rinton Press. - 1533-7146. ; 14:3-4, s. 339-360
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Tidskriftsartikel (refereegranskat)abstract
- It is known that if the dimension is a perfect square the Clifford group can be represented by monomial matrices. Another way of expressing this result is to say that when the dimension is a perfect square the standard representation of the Clifford group has a system of imprimitivity consisting of one dimensional subspaces. We generalize this result to the case of an arbitrary dimension. Let k be the square-free part of the dimension. Then we show that the standard representation of the Clifford group has a system of imprimitivity consisting of k-dimensional subspaces. To illustrate the use of this result we apply it to the calculation of SIC-POVMs (symmetric informationally complete positive operator valued measures), constructing exact solutions in dimensions 8 (hand-calculation) as well as 12 and 28 (machine-calculation).
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| 9. |
- Appleby, D. M., et al.
(författare)
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The monomial representations of the Clifford group
- 2012
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Ingår i: Quantum information & computation. - : Rinton Press, Inc.. - 1533-7146. ; 12:5-6, s. 404-431
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Tidskriftsartikel (refereegranskat)abstract
- We show that the Clifford group-the normaliser of the Weyl-Heisenberg group-can be represented by monomial phase-permutation matrices if and only if the dimension is a square number. This simplifies expressions for SIC vectors, and has other applications to SICs and to Mutually Unbiased Bases. Exact solutions for SICs in dimension 16 are presented for the first time.
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| 10. |
- Appleby, Marcus, et al.
(författare)
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Dimension towers of SICs. I. Aligned SICs and embedded tight frames
- 2017
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Ingår i: Journal of Mathematical Physics. - : AIP Publishing. - 0022-2488 .- 1089-7658. ; 58:11
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Tidskriftsartikel (refereegranskat)abstract
- Algebraic number theory relates SIC-POVMsin dimension d > 3 to those in dimension d(d - 2). We define a SIC in dimension d(d - 2) to be aligned to a SIC in dimension d if and only if the squares of the overlap phases in dimension d appear as a subset of the overlap phases in dimension d(d - 2) in a specifiedway. We give 19 (mostly numerical) examples of aligned SICs. We conjecture that given any SIC in dimension d, there exists an aligned SIC in dimension d(d - 2). In all our examples, the aligned SIC has lower dimensional equiangular tight frames embedded in it. If d is odd so that a natural tensor product structure exists, we prove that the individual vectors in the aligned SIC have a very special entanglement structure, and the existence of the embedded tight frames follows as a theorem. If d - 2 is an odd prime number, we prove that a complete set of mutually unbiased bases can be obtained by reducing an aligned SIC to this dimension.
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