Proposal for detection of non-Markovian decay via current noise

Abstract

We propose to detect non-Markovian decay of an exciton qubit coupled to multi-mode bosonic reservoir via shot-noise measurements. Non-equilibrium current noise is calculated for a quantum dot embedded inside a p-i-n junction. An additional term from non-Markovian effect is obtained in the derivation of noise spectrum. As examples, two practical photonic reservoirs, photon vacuum with the inclusion of cut-off frequency and surface plasmons, are given to show that the noise may become super-Poissonian due to this non-Markovian effect. Utilizing the property of super-radiance is further suggested to enhance the noise value.PACS numbers: 03.65. Yz, 72.70.+m, 73.20.Mf, Introduction.-Due to rapid progress of quantum information science, great attention has been focused on the dynamics of systems interacting with their surroundings. Radiative decay of a two-level atom maybe one of the most obvious examples in this issue and can be traced back to such early works as that of Albert Einstein in 1917.[1] While Markovian approximation is widely adopted to treat decoherence and relaxation problems, non-Markovian dynamics of qubit systems have attracted increasing attention lately. [2] Turning to solid state systems, an exciton in a quantum dot (QD) can be viewed as a two-level system. Radiative properties of QD excitons, such as super-radiance [3] and Purcell effect [4], have attracted great attention during the past two decades. Utilizing QD excitons for quantum gate operations have also been demonstrated experimentally.[5] With the advances of fabrication technologies, it is now possible to embed QDs inside a p-i-n structure [6], such that the electron and hole can be injected separately from opposite sides. This allows one to examine the exciton dynamics in a QD via electrical currents [7].Recently, the interest in measurements of shot noise in quantum transport has risen owing to the possibility of extracting valuable information not available in conventional dc transport experiments [8]. In this work, we propose to detect non-Markovian decay of a exciton qubit via the current noise of a QD p-i-n junction. Without making Markovian approximation to the exciton-boson interaction, we analytically show that the Fano factor (zero-frequency noise) may become super-Poissonian. As examples, two practical photonic environments, photon vacuum with the inclusion of cut-off frequency and surface plasmons, are given to show this non-Markovian effect. To enhance the noise value, we further suggest utilizing the property of super-radiance.The model.-QDs can now be embedded in a p-i-n junction, such that many applications can be accomplished by electrical control. As shown in Fig. 1, we wish to see

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