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We are pleased to announce a Sabarmati Seminar by Dr. Archak Purkayastha, a post-doctoral fellow in the group of John Goold at Trinity College, Dublin. Please find the title,abstract for the talk, and a short bio of the speaker below. 

Title: Generating steady state coherence a solid state qubit using quantum noise from phonons

Coordinates: 09 Jan 2020, 7/210

Abstract: Much of quantum technology depends on generation and control of coherence in a qubit. In particular, coherence in the energy eigenbasis of a system has been recognized as a resource. However, coherence in energy eigenbasis is usually fragile. Interaction of the system with its surrounding environment provides noise in the qubit parameters, which in turn is thought to lead to decoherence, i.e, loss of coherence in the energy eigenbasis. In this talk, I will show that while this is true for classical noise in qubit parameters, quantum noise in qubit parameters actually generates coherence in the energy eigenbasis of the qubit under generic conditions. This coherence occurs in the steady state and is therefore robust. This is particularly interesting in the context of  a solid state double-quantum-dot (DQD) charge qubit where quantum noise from phonons in the substrate is the leading source of noise. Moreover, the DQD charge qubit is widely tunable, and by controlling its parameters, regimes of high purity along with coherence in energy eigenbasis can be found. The coherence is robust to presence of fermionic leads at equilbrium, and can be used to displace a cavity mode.

Bio: Archak graduated with Bachelors degree in Physics from Jadavpur University, Kolkata, in 2011, followed by a Masters Degree in Physics from Indian Institute of Technology, Kanpur, in 2013. Then he did his Ph.D at the International Centre for Theoretical Sciences, Tata Institute for Fundamental Research (ICTS-TIFR), Bangalore, under the supervision of Prof. Abhishek Dhar. He defended his PhD in September, 2018. He stayed at ICTS-TIFR till December, 2018 as a visiting-fellow. From Feb 1, 2019, he has joined the QuSys team of John Goold at Trinity College, Dublin for his post-doctoral research. During his PhD, he has developed expertise in the formalism for investigating transport phenomena in open quantum systems. In Dublin he is exploring thermodynamics of open quantum systems, and applications of open quantum systems in building, for example, quantum engines and sensors.

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