Full quantum state reconstruction of symmetric two-mode squeezed thermal states via spectral homodyne detection and a state-balancing detector

Abstract

We suggest and demonstrate a scheme to reconstruct the symmetric two-mode squeezed thermal states of spectral sideband modes from an optical parametric oscillator. The method is based on a single homodyne detector and active stabilization of the cavity. The measurement scheme have been successfully tested on different two-mode squeezed thermal states, ranging from uncorrelated coherent states to entangled states.PACS numbers: 03.65. Wj, 42.50.Lc, 42.50.Dv Introduction -Homodyne detection (HD) is an effective tool to characterize the quantum state of light in either the time [1][2][3][4][5][6][7][8] or the frequency [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] domain. In a spectral homodyne detector, the signal under investigation interferes at a balanced beam splitter with a local oscillator (LO) with frequency ω 0 . The two outputs undergo a photodetection process and their photocurrents are combined leading to a photocurrent continuously varying in time. The information about the spectral field modes at frequencies ω 0 ± Ω (sidebands) is then retrieved by electronically mixing the photocurrent with a reference signal with frequency Ω and phase Ψ. Upon varying the phase θ of the LO, we may access different field quadratures, whereas the phase Ψ can be adjusted to select the symmetric S or antisymmetric A balanced combinations of the upper and lower sideband modes.

Squeezing Phase Diffusion

“…The role of the transmissivities will be clear later. The cavity is actively stabilized using the Pound-Drever-Hall (PDH) technique [26] by means of a phase modulator (PM) placed along the SG beam, which generates two 116 MHz sidebands around the laser frequency. Coherent states are generated exploiting the combined effect of two optical modulators (MOD1 and MOD2) placed before the OPO.…”

“…Coherent states are generated exploiting the combined effect of two optical modulators (MOD1 and MOD2) placed before the OPO. A proper choice of their modulations allows us to generate an arbitrary coherent state on the sidebands at 3 MHz for seeding the OPO [25,26]. Amplitude and phase values are set on demand by a computer.…”

Quantum tomography of light states by photon-number-resolving detectors

“…Usually, the homodyne probability distributions p(x, f) are retrieved from the difference of the two macroscopic photocurrents exiting the homodyne detector [40][41][42]. In our scheme, we replace p(…”

Experimental quantum tomography of a homodyne detector

“…Balanced homodyne detection is a crucial detection technique for continuous variable quantum technology and lies at the core of many experiments in fundamental quantum optics [1][2][3]. From its first proposal for the measurement of quadrature squeezing, to its current extensive use in the fields of quantum tomography, quantum communication and quantum metrology [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18], this detection scheme has carved its place into experimental quantum optics. Besides quantum optical systems, homodyne detection extends its reach to the whole field of continuous variable quantum technologies, spanning from atomic systems [19,20] to quantum optomechanics [21].…”