996 research outputs found
Benchmarking high fidelity single-shot readout of semiconductor qubits
Determination of qubit initialisation and measurement fidelity is important
for the overall performance of a quantum computer. However, the method by which
it is calculated in semiconductor qubits varies between experiments. In this
paper we present a full theoretical analysis of electronic single-shot readout
and describe critical parameters to achieve high fidelity readout. In
particular, we derive a model for energy selective state readout based on a
charge detector response and examine how to optimise the fidelity by choosing
correct experimental parameters. Although we focus on single electron spin
readout, the theory presented can be applied to other electronic readout
techniques in semiconductors that use a reservoir.Comment: 19 pages, 8 figure
Reasoning with comparative moral judgements: an argument for Moral Bayesianism
The paper discusses the notion of reasoning with comparative moral judgements
(i.e judgements of the form âact a is morally superior to act bâ) from the point of view of several meta-ethical positions. Using a simple formal result, it is argued that only a version of moral cognitivism that is committed to the claim that moral beliefs come in degrees can give a normatively plausible account of such reasoning. Some implications of accepting such a version of moral cognitivism are discussed
Diphacinone and coumatetralyl persistence in deer and implications for wildlife management
Eason, C.T., Murphy, E., Ross, J.G., Hix, S., Arthur, D., MacMorran, D., Broome, K., Fairweather, A
Rationality as the Rule of Reason
The demands of rationality are linked both to our subjective normative perspective (given that rationality is a person-level concept) and to objective reasons or favoring relations (given that rationality is non-contingently authoritative for us). In this paper, I propose a new way of reconciling the tension between these two aspects: roughly, what rationality requires of us is having the attitudes that correspond to our take on reasons in the light of our evidence, but only if it is competent. I show how this view can account for structural rationality on the assumption that intentions and beliefs as such involve competent perceptions of downstream reasons, and explore various implications of the account
Tunneling statistics for analysis of spin-readout fidelity
We investigate spin and charge dynamics of a quantum dot of phosphorus atoms
coupled to a radio-frequency single-electron transistor (rf-SET) using full
counting statistics. We show how the magnetic field plays a role in determining
the bunching or anti-bunching tunnelling statistics of the donor dot and SET
system. Using the counting statistics we show how to determine the lowest
magnetic field where spin-readout is possible. We then show how such a
measurement can be used to investigate and optimise single electron
spin-readout fidelity.Comment: 11 pages, 6 figure
High-fidelity single-shot singlet-triplet readout of precision-placed donors in silicon
In this work we perform direct single-shot readout of the singlet-triplet states in exchange coupled electrons confined to precision-placed donor atoms in silicon. Our method takes advantage of the large energy splitting given by the Pauli-spin blockaded (2,0) triplet states, from which we can achieve a single-shot readout fidelity of 98.4 ± 0.2%. We measure the triplet-minus relaxation time to be of the order 3 s at 2.5 T and observe its predicted decrease as a function of magnetic field, reaching 0.5 s at 1 T
Delusional beliefs and reason giving
Delusions are often regarded as irrational beliefs, but their irrationality is not sufficient to explain what is pathological about them. In this paper we ask whether deluded subjects have the capacity to support the content of their delusions with reasons, that is, whether they can author their delusional states. The hypothesis that delusions are characterised by a failure of authorship, which is a dimension of self knowledge, deserves to be
empirically tested because (a) it has the potential to account for the distinction between endorsing a delusion and endorsing a framework belief; (b) it contributes to a
philosophical analysis of the relationship between rationality and self knowledge; and (c) it informs diagnosis and therapy in clinical psychiatry. However, authorship cannot provide a demarcation criterion between delusions and other irrational belief states
Extracting inter-dot tunnel couplings between few donor quantum dots in silicon
The long term scaling prospects for solid-state quantum computing architectures relies heavily on the
ability to simply and reliably measure and control the coherent electron interaction strength, known
as the tunnel coupling, tc. Here, we describe a method to extract the tc between two quantum dots
(QDs) utilising their different tunnel rates to a reservoir. We demonstrate the technique on a few
donor triple QD tunnel coupled to a nearby single-electron transistor(SET)in silicon. The device was
patterned using scanning tunneling microscopy-hydrogen lithography allowing for a direct
measurement of the tunnel coupling for a given inter-dot distance. We extract tc = ± 5.5 1.8 GHz
and tc = ± 2.2 1.3 GHz between each of the nearest-neighbour QDs which are separated by 14.5 nm
and 14.0 nm, respectively. The technique allows for an accurate measurement of tc for nanoscale
devices even when it is smaller than the electron temperature and is an ideal characterisation tool for
multi-dot systems with a charge senso
Addressable electron spin resonance using donors and donor molecules in silicos
Phosphorus donor impurities in silicon are a promising candidate for solid-state quantum computing due to their exceptionally long coherence times and high fidelities. However, individual addressability of exchange coupled donors with separations ~15 nm is challenging. We show that by using atomic precision lithography, we can place a single P donor next to a 2P molecule 16 ± 1 nm apart and use their distinctive hyperfine coupling strengths to address qubits at vastly different resonance frequencies. In particular, the single donor yields two hyperfine peaks separated by 97 ± 2.5 MHz, in contrast to the donor molecule that exhibits three peaks separated by 262 ± 10 MHz. Atomistic tight-binding simulations confirm the large hyperfine interaction strength in the 2P molecule with an interdonor separation of ~0.7 nm, consistent with lithographic scanning tunneling microscopy images of the 2P site during device fabrication. We discuss the viability of using donor molecules for built-in addressability of electron spin qubits in silicon
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