Quantum witness of a damped and driven qubit by sequential intermediate measurements with uniform and nonuniform time in
- PDF / 2,593,087 Bytes
- 15 Pages / 439.37 x 666.142 pts Page_size
- 33 Downloads / 164 Views
Quantum witness of a damped and driven qubit by sequential intermediate measurements with uniform and nonuniform time intervals Longyan Gong1 · Kaixin Ma1,2 · Xiaoxin Zhao1,2 · Weiwen Cheng2 · Shengmei Zhao2 Received: 22 May 2019 / Accepted: 13 July 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Measurement can reveal the difference between quantum physics and classical one. Recently, a quantum witness Wq was proposed to characterize quantumness (Li et al. in Sci Rep 2:885, 2012; Kofler and Brukner in Phys Rev A 87:052115, 2013). It is built upon the no-signaling-in-time condition, and there is only one-time intermediate measurement. As an extension, we consider here multiple intermediate measurements at different moments of time. And we discuss the quantumness of a damped and driven qubit. Uniform, quasiperiodic and random time-interval sequences (TISs) of measurements are considered, respectively. Numerical results show that Wq depends on the kind of TISs when the number of measurements N is less than 10, while it is almost independent of the kind of TISs when N is larger. Further, Wq ≤ Wqmax (N ) = 1 (1 − 2N )e−γ τ for all cases, where τ is the evolution time, γ is the dephasing intensity, max and Wq (N ) is the maximum violation of the quantum witness equality. Keywords Quantumness · Quantum witness · Damped and driven qubit
1 Introduction In the past one hundred years, uncertainty, complementarity, coherence, superposition and entanglement are often discussed in-depth [1–3]. They may represent the main differences between quantum physics and classical one [4]. Quantum information technologies [5], such as quantum communication [6], quantum computation [7] and
B
Longyan Gong [email protected]
1
New energy technology Engineering of Jiangsu province and College of science, Nanjing University of Posts and Telecommunications, Nanjing 210003, China
2
Institute of Signal Processing and Transmission, Nanjing University of Posts and Telecommunications, Nanjing 210003, China 0123456789().: V,-vol
123
260
Page 2 of 15
L. Gong et al.
quantum metrology [8], heavily rely on these features. Therefore, it is essential to assess the quantumness of a physical system [9]. Measurements play a significant role in physics. In classical physics, an ideal measurement can be carried out without perturbing systems and results are determined with certainty. For instance, the exact position and momentum of a classical particle can be simultaneously determined. However, a quantum measurement will disturb systems due to the quantum superposition principle, uncertainty principle and quantum collapse, so noncommutative quantities cannot be simultaneously determined [10,11]. In order to characterize system properties, multiple measurements at different moments of time should be done on the same ensemble, then the probability distribution of each measurement outcome can be obtained. Therefore, an appropriate measurement can reveal the difference between quantum physics and classical one [12,1
Data Loading...
