scholarly journals Optimal estimation of quantum processes using incomplete information: variational quantum process tomography

2012 ◽  
Vol 12 (5&6) ◽  
pp. 442-447
Author(s):  
Thiago O. Maciel ◽  
Reinaldo O. Vianna
Keyword(s):  
Incomplete Information ◽  
Optimal Estimation ◽  
Quantum Tomography ◽  
New Method ◽  
Quantum Processes ◽  
Quantum Process ◽  
Quantum Process Tomography ◽  
Process Tomography ◽  
Tomography Method

We develop a quantum process tomography method, which variationally reconstruct the map of a process, using noisy and incomplete information about the dynamics. The new method encompasses the most common quantum process tomography schemes. It is based on the variational quantum tomography method (VQT) proposed by Maciel \emph{et al.} in arXiv:1001.1793[quant-ph] \cite{VQT}.

scholarly journals Guaranteed recovery of quantum processes from few measurements

Quantum ◽  
2019 ◽  
Vol 3 ◽  
pp. 171 ◽  
Author(s):  
Martin Kliesch ◽  
Richard Kueng ◽  
Jens Eisert ◽  
David Gross
Keyword(s):  
A Priori ◽  
Measurement Model ◽  
Low Rank ◽  
Quantum Channels ◽  
Reconstruction Algorithms ◽  
Quantum Processes ◽  
Quantum Process ◽  
Multiple Channel ◽  
Quantum Process Tomography ◽  
Process Tomography

Quantum process tomography is the task of reconstructing unknown quantum channels from measured data. In this work, we introduce compressed sensing-based methods that facilitate the reconstruction of quantum channels of low Kraus rank. Our main contribution is the analysis of a natural measurement model for this task: We assume that data is obtained by sending pure states into the channel and measuring expectation values on the output. Neither ancillary systems nor coherent operations across multiple channel uses are required. Most previous results on compressed process reconstruction reduce the problem to quantum state tomography on the channel's Choi matrix. While this ansatz yields recovery guarantees from an essentially minimal number of measurements, physical implementations of such schemes would typically involve ancillary systems. A priori, it is unclear whether a measurement model tailored directly to quantum process tomography might require more measurements. We establish that this is not the case.Technically, we prove recovery guarantees for three different reconstruction algorithms. The reconstructions are based on a trace, diamond, and ℓ2-norm minimization, respectively. Our recovery guarantees are uniform in the sense that with one random choice of measurement settings all quantum channels can be recovered equally well. Moreover, stability against arbitrary measurement noise and robustness against violations of the low-rank assumption is guaranteed. Numerical studies demonstrate the feasibility of the approach.

scholarly journals Ancilla-Assisted Quantum Process Tomography

2003 ◽  
Vol 90 (19) ◽  
Author(s):  
J. B. Altepeter ◽  
D. Branning ◽  
E. Jeffrey ◽  
T. C. Wei ◽  
P. G. Kwiat ◽  
...  
Keyword(s):  
Quantum Process ◽  
Quantum Process Tomography ◽  
Process Tomography

scholarly journals Characterizing d-dimensional quantum channels by means of quantum process tomography

2018 ◽  
Vol 43 (18) ◽  
pp. 4398 ◽  
Author(s):  
J. J. M. Varga ◽  
L. Rebón ◽  
Q. Pears Stefano ◽  
C. Iemmi
Keyword(s):  
Quantum Channels ◽  
Quantum Process ◽  
Quantum Process Tomography ◽  
Process Tomography

scholarly journals Detection of Properties and Capacities of Quantum Channels

2017 ◽  
Vol 24 (04) ◽  
pp. 1740013 ◽  
Author(s):  
Chiara Macchiavello ◽  
Massimiliano F. Sacchi
Keyword(s):  
Entangled State ◽  
Quantum Channels ◽  
Quantum Process ◽  
Channel Output ◽  
Quantum Process Tomography ◽  
Channel Input ◽  
Process Tomography ◽  
Local Measurements ◽  
System States ◽  
Full Quantum

We review in a unified way a recently proposed method to detect properties of unknown quantum channels and lower bounds to quantum capacities, without resorting to full quantum process tomography. The method is based on the preparation of a fixed bipartite entangled state at the channel input or, equivalently, an ensemble of an overcomplete set of single-system states, along with few local measurements at the channel output.

scholarly journals Quantum Process Tomography of a Controlled-Phase Gate for Time-Bin Qubits

2020 ◽  
Vol 13 (3) ◽  
Author(s):  
Hsin-Pin Lo ◽  
Takuya Ikuta ◽  
Nobuyuki Matsuda ◽  
Toshimori Honjo ◽  
William J. Munro ◽  
...  
Keyword(s):  
Quantum Process ◽  
Quantum Process Tomography ◽  
Process Tomography ◽  
Phase Gate ◽  
Controlled Phase Gate

scholarly journals Characterization of depolarizing channels using two-photon interference

2019 ◽  
Vol 18 (11) ◽  
Author(s):  
G. C. Amaral ◽  
G. P. Temporão
Keyword(s):  
Quantum Communication ◽  
Communication Link ◽  
Time Varying ◽  
Quantum Process ◽  
Standard Quantum ◽  
Two Photon ◽  
Quantum Process Tomography ◽  
Process Tomography ◽  
Unitary Transformations

Abstract Depolarization is one of the most important sources of error in a quantum communication link that can be introduced by the quantum channel. Even though standard quantum process tomography can, in theory, be applied to characterize this effect, in most real-world implementations depolarization cannot be distinguished from time-varying unitary transformations, especially when the timescales are much shorter than the detectors response time. In this paper, we introduce a method for distinguishing true depolarization from fast polarization rotations by employing Hong–Ou–Mandel interference. It is shown that the results are independent of the timing resolutions of the photodetectors.

Experimental demonstration of optimized quantum process tomography on the IBM quantum experience

2020 ◽  
pp. 2040004
Author(s):  
Akshay Gaikwad ◽  
Krishna Shende ◽  
Kavita Dorai
Keyword(s):  
Quantum Circuit ◽  
Quantum Gates ◽  
Experimental Demonstration ◽  
Superconducting Qubit ◽  
Quantum Process ◽  
Single Qubit ◽  
Quantum Process Tomography ◽  
Process Tomography ◽  
Quantum Processor ◽  
Least Squares Optimization

We experimentally performed complete and optimized quantum process tomography of quantum gates implemented on superconducting qubit-based IBM QX2 quantum processor via two constrained convex optimization (CCO) techniques: least squares optimization and compressed sensing optimization. We studied the performance of these methods by comparing the experimental complexity involved and the experimental fidelities obtained. We experimentally characterized several two-qubit quantum gates: identity gate, a controlled-NOT gate, and a SWAP gate. The general quantum circuit is efficient in the sense that the data needed to perform CCO-based process tomography can be directly acquired by measuring only a single qubit. The quantum circuit can be extended to higher dimensions and is also valid for other experimental platforms.

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