Interferometry of non-Abelian anyons Bonderson, Parsa; Shtengel, Kirill; Slingerland, J.K.
Annals of physics,
11/2008, Letnik:
323, Številka:
11
Journal Article
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Odprti dostop
We develop the general quantum measurement theory of non-Abelian anyons through interference experiments. The paper starts with a terse introduction to the theory of anyon models, focusing on the ...basic formalism necessary to apply standard quantum measurement theory to such systems. This is then applied to give a detailed analysis of anyonic charge measurements using a Mach–Zehnder interferometer for arbitrary anyon models. We find that, as anyonic probes are sent through the legs of the interferometer, superpositions of the total anyonic charge located in the target region collapse when they are distinguishable via monodromy with the probe anyons, which also determines the rate of collapse. We give estimates on the number of probes needed to obtain a desired confidence level for the measurement outcome distinguishing between charges, and explicitly work out a number of examples for some significant anyon models. We apply the same techniques to describe interferometry measurements in a double point-contact interferometer realized in fractional quantum Hall systems. To lowest order in tunneling, these results essentially match those from the Mach–Zehnder interferometer, but we also provide the corrections due to processes involving multiple tunnelings. Finally, we give explicit predictions describing state measurements for experiments in the Abelian hierarchy states, the non-Abelian Moore–Read state at
ν
=
5
/
2
and Read–Rezayi state at
ν
=
12
/
5
.
We examine interferometric experiments in systems that exhibit non-Abelian braiding statistics, expressing outcomes in terms of the modular S-matrix. In particular, this result applies to fractional ...quantum Hall interferometry, and we give a detailed treatment of the Read-Rezayi states, providing explicit predictions for the recently observed nu = 12/5 plateau.
We examine interferometric measurements of the topological charge of (non-Abelian) anyons. The target's topological charge is measured from its effect on the interference of probe particles sent ...through the interferometer. We find that superpositions of distinct anyonic charges a and a' in the target decohere (exponentially in the number of probes particles used) when the probes have nontrivial monodromy with the charges that may be fused with a to give a'.
In this paper, we study both experimentally and theoretically how the change of the p-doping profile, particularly the p-i junction placement, affects the output characteristics of 1.3- mu m ...InGaAsP-InP multiple-quantum-well (MQW) lasers. The relationship between the p-doping profile before and after regrowth is established, and the subsequent impact of changes in the p-i junction placement on the device output characteristics, is demonstrated. Device characteristics are simulated including carrier transport, capture of carriers into the quantum wells, the quantum mechanical calculation of the properties of the wells, and the solution for the optical mode and its population self-consistently as a function of diode bias. The simulations predict and the experiments confirm that an optimum p-i junction placement simultaneously maximizes external efficiency and minimizes threshold current. Tuning of the base epitaxial growth Zn profile allows one to fabricate MQW devices with a threshold current of approximately 80 A/cm super(2) per well for devices with nine QW's at room temperature or lasers with a characteristic temperature T sub(0)=70 K within the temperature range of 20 degree C-80 degree C
We describe the important characteristics of high-speed p-doped compressively strained MQW lasers obtained from comprehensive below-threshold DC measurements. Results of gain and differential gain ...versus wavelength and carrier density are verified by above-threshold resonance measurements. Measurement-derived design curves of gain, differential gain, and linewidth enhancement factor allow device optimization for high speed and low chirp.< >
In this paper, we study both experimentally and theoretically how the change of the p-doping profile, particularly the p-i junction placement, affects the output characteristics of 1.3-mum ...InGaAsP-InP multiple-quantum-well (MQW) lasers. The relationship between the p-doping profile before and after regrowth is established, and the subsequent impact of changes in the p-i junction placement on the device output characteristics, is demonstrated. Device characteristics are simulated including carrier transport, capture of carriers into the quantum wells, the quantum mechanical calculation of the properties of the wells, and the solution for the optical mode and its population self-consistently as a function of diode bias. The simulations predict and the experiments confirm that an optimum p-i junction placement simultaneously maximizes external efficiency and minimizes threshold current. Tuning of the base epitaxial growth Zn profile allows one to fabricate MQW devices with a threshold current of approximately 80 A/cm (2) per well for devices with nine QW's at room temperature or lasers with a characteristic temperature T(0)=70 K within the temperature range of 20 deg C-80 deg C
We have developed a microscopic model for a semiconductor diode laser which includes the physical transport of carriers, the quantum processes associated with the quantum wells (capture and gain) and ...the photon modes, all self consistently as a function of the device bias. Detailed comparison to experiment for electrical and optical properties shows the reliability of the model. Simulation shows that in a conventional multi-quantum well active layer device, the carrier distribution among the wells can be quite non-uniform. We propose that this is the fundamental explanation for the dependence of high speed operation on p-doping.
Summary form only given. A maximum bandwidth of 14 GHz was observed in a study of small-diameter vertical-cavity surface emitting lasers (VCSELs). Gain-guided VCSELs from two wafers were used, ...nominally lasing at either 780 nm or 960 nm. Modulation experiments showed a very high frequency-square root of power coefficient D=10 GHz/mW/sup 1/2/. The maximum bandwidth of 13.7 GHz was reached at 20 degrees C (and 14.7 GHz at 7 degrees C) at a current of 8 mA for the 780 nm laser with a cavity diameter of 6 mu m. The cavity region of these lasers received both a broad area proton implant and a second deep implant centered at the active region to better define the cavity diameter. The 960 nm lasers received only the first broad area implant and their measured response of 10 GHz indicates the importance of minimizing lateral carrier diffusion.< >
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