Programme

O.9 -- Oral, VCTP-44

Date: Tuesday, 30 July 2019

Time: 11:00 - 11:20

Probe-controlled-system approach to direct state measurement

Kieu Quang Tuan (1), Hung Quoc Nguyen (2), and Le Bin Ho (3)(4)

(1) Department of Theoretical Physics, University of Science, Ho Chi Minh City, Vietnam (2) Nano and Energy Center, VNU University of Science, Hanoi, Vietnam (3) Ho Chi Minh City Institute of Physics, VAST, Vietnam (4) Department of Physics, Kindai University, Higashi-Osaka 577-8502, Japan

A complex wave function in quantum mechanics is the fundamental representation of the quantum state of a system. In its statistical interpretation, the wave function predicts the results of measurements made on the system. Therefore, a complete determination of the wave function, or in general, the density matrix, of quantum states is crucially important and is one of the main tasks in quantum mechanics. In practice, quantum state tomography (QST) is widely employed for quantum state measurements. This method measures multiple copies of the system in a complete set of non-commuting observables, which is used to reconstruct the quantum state. It is, however, difficult to apply in large systems where exponentially complicated calculations and precise measurements are required. Alternatively, one can use direct state measurement [1, 2]. Here, the system of interested interacts with a pointer to obtain weak value, which are proportional to the amplitude of the wave functions. So far, the DSM approach has been verified based on weak interaction [2], arbitrary strong interaction [3], coupling-deformed pointer observables [4], and enlarged Hilbert spaces [5]. In this work, we focus on the DSM using the probe-controlled-system method [6]. This approach uses a probe-controlled-system transformation instead of a system-probe interaction to obtain the desired quantum state. We first analyze the precision of our approach in comparison to the weak- and strong-measurement approaches. Then, we present our simulation and analytic calculation results. We believe that this approach provides a simpler and more effective tool to measure the quantum wave function directly. [1] J. S. Lundeen, B. Sutherland, A. Patel, C. Stewart, and C. Bamber, Nature 474, 188 (2011). [2] Salvail et al., Nat. Photon. 7, 316 (2013).; Malik et al., Nat. Comm. 5 (2014).; Bolduc et al., Nat. Commun. 7 (2016).; Thekkadath et al., Phys. Rev. Lett. 117, 120401 (2016). [3] G. Vallone and D. Dequal, Phys. Rev. Lett. 116, 040502 (2016).; Denkmayr et al., Phys. Rev. Lett. 118, 010402 (2017). [4] Zhang et al., Phys. Rev. A 93, 032128 (2016).; Zhu et al., Phys. Rev. A 93, 062304 (2016). [5] L. B. Ho and N. Imoto, Phys. Rev. A 97, 012112 (2018).; L. B. Ho, Phys. Lett. A 383, 289 (2019). [6] K. Ogawa, O. Yasuhiko, H. Kobayashi, T. Nakanishi, and A. Tomita, New J. Phys. 21, 043013 (2019).

Presenter: Kieu Quang Tuan