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QUANTUM STATE TOMOGRAPHY OF SINGLE QUBITWITH LASER IR 808nm USING DENSITY MATRIX

Syafi’i Fahmi Bastian

Published Sep 12, 2019• 0 citations
OpenAlex

Abstract

The quantum state tomography is an essential component in the development of quantum technologies. It is a representation of polarization state which can be used to know the characterization of small particle called photon in the nanoscale. In this research, photon number has been measured in order to create the states tomography. Optical devices and quantum-mechanical approaches were used to accomplish the image of quantum state tomography. Due to a single qubit state density matrix can be represented by Stokes parameters, so there are four set-ups to measure the Stokes parameters for each sample. The density matrix in this work is used because the pure state only happen in theoretical idea. And in the real experiment, It always shows a mixed state. The density matrix will represent seven samples in this work. The samples of tomography measurements consist of horizontal state, vertical state, diagonal state, anti-diagonal state, right-circular state, left-circular state and the tomography of laser IR 808nm. In this work, state tomography is shown by 2x2 density matrix. This research also shows the fidelities between theory and experiment result. And it shows the good agreement. From this research, the state of laser beam has known. The laser that used is showing a vertical state with fidelity F=97,34%.

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The quantum state tomography is an essential component in the development of
quantum technologies. It is a representation of polarization state which can be used
to know the characterization of small particle called photon in the nanoscale. In
this research, photon number has been measured in order to create the states
tomography. Optical devices and quantum-mechanical approaches were used to
accomplish the image of quantum state tomography. Due to a single qubit state
density matrix can be represented by Stokes parameters, so there are four set-ups
to measure the Stokes parameters for each sample. The density matrix in this work
is used because the pure state only happen in theoretical idea. And in the real
experiment, It always shows a mixed state. The density matrix will represent
seven samples in this work. The samples of tomography measurements consist of
horizontal state, vertical state, diagonal state, anti-diagonal state, right-circular
state, left-circular state and the tomography of laser IR 808nm. In this work, state
tomography is shown by 2x2 density matrix. This research also shows the
fidelities between theory and experiment result. And it shows the good agreement.
From this research, the state of laser beam has known. The laser that used is
showing a vertical state with fidelity F=97,34%.
Abstract. The quantum state tomography is a fundamental part in the development of quantum technologies. It can be used to know the signal characterization of small particle called photon in the nanoscale. In this study, photon number has been measured in order to produce the states tomography. Optical devices and quantum-mechanical approaches were explored to obtain the quantum state tomography. Due to a single qubit state density matrix can be revealed by Stokes parameters, so there are four set-ups to measure the Stokes parameters for each sample. The density matrix is used because the pure state only appear theoreticaly. In the real experiment, It always exibits a mixed state. The samples of tomography measurements consist of linear state, cicular state and the IR 808nm. In this study, state tomography is shown by 2x2 density matrix. This experiment also provides the fidelities of experiment result. And it shows the good agreement. From this experiment, the state of IR 808nm has been detected. The laser that examined is showing a vertical state with fidelity F=97,34%.
Quantum state tomography (QST), the process through which the density matrix of a quantum system is characterized from measurements of specific observables, is a fundamental pillar in the fields of quantum information and computation. In this work, we propose a simple QST method to reconstruct the density matrix of two qubits encoded in the polarization and path degrees of freedom of a single photon, which can be realized with a single linear-optical setup. We demonstrate that the density matrix can be fully described in terms of the Stokes parameters related to the two possibles paths of the photon, together with a quantum version of the two-point Stokes parameters introduced here. Our findings put forward photonic circuits for the investigation of the dynamics of open quantum systems.
Quantum state tomography (QST), the process through which the density matrix of a quantum system is characterized from measurements of specific observables, is a fundamental pillar in the fields of quantum information and computation. In this work, we propose a simple QST method to reconstruct the density matrix of two qubits encoded in the polarization and path degrees of freedom of a single photon, which can be realized with a single linear-optical setup. We demonstrate that the density matrix can be fully described in terms of the Stokes parameters related to the two possible paths of the photon, together with a quantum version of the two-point Stokes parameters introduced here. Our findings put forward photonic circuits for the investigation of the dynamics of open quantum systems.
We propose a technique for performing quantum state tomography of photonic polarization-encoded multiqubit states. Our method uses a single rotating wave plate, a polarizing beam splitter, and two photon-counting detectors per photon mode. As the wave plate rotates, the photon counters measure a pseudocontinuous signal which is then Fourier transformed. The density matrix of the state is reconstructed using the relationship between the Fourier coefficients of the signal and the Stokes' parameters that represent the state. The experimental complexity, i.e., different wave plate rotation frequencies, scales linearly with the number of qubits.
Quantum state tomography (QST) is an executable procedure, allowing complete reconstruction of a quantum state. As a basic tool, QST is widely employed in quantum information research. However, many projective measurements on identical copies of the quantum state under test are required in standard QST, which is heavily time-consumed. Here, we perform reconstruction of density matrix with dimensionality of 15×1515\times 1515×15 by utilizing compressed sensing method at a sampling ratio of 0.35. According to the experimental results, the fidelity could be as high as 93.0%~99.4% and 73.8% for coherent laser beams and heralded single photon sources, respectively.
Tomography allows one to estimate the density matrix describing the state an ensemble of quantum systems are prepared in (for example, polarization tomography determines the polarization state of a beam of identically prepared photons). In general, it is not possible to uniquely decompose the density matrix into its pure state components. Agarwal et al. proposed a protocol which, for a mixture composed of any two pure states of a qubit (with arbitrary probabilities), allows an observer to infer not only the density matrix but the identity of those specific pure states and their weights - the additional requirement being that the qubits arrive in pairs, where both qubits in each pair are in the same state. We experimentally demonstrate this learning-from-pairs concept using photons in the polarization degree of freedom. We use tomography to measure a sequence of single photons and make use of their time-of-arrival information to 'pair up' the photons after the measurement. From here we are able to infer the photons' polarization states and their respective probabilities, and we demonstrate this for various different choices of polarization states and ratios. Finally, we investigate our ability to discriminate between two equal mixtures of distinct pairs of orthogonal polarization states. We find that on the order of approx. 10e4 photons is typically enough to achieve tomography fidelities of approximately 0.9999. This is sufficient to discriminate between two different preparations of the same mixed state, differing by angles of less than 5 degrees between the pure states used in the two preparations.