Quantum State Engineering of Light with Continuous-wave Optical Parametric Oscillators

The goal of this experiment is to generate non Gaussian states of traveling optical fields with high fidelity, including single photon and coherent state super positions known as Schrodinger CAT states. This is achieved by using non-classical correlated beams as a primary light source. As a second step, a single photon is detected on one beam, which results in projecting the other beam in a heralded conditional quantum state.

This is known as the conditional preparation technique where an initial Gaussian resource is combined with a non Gaussian measurement such as photon counting. Next, the heralded state is measured by homo dyne detection in order to perform the full quantum state tomography. Ultimately, results are obtained that show high fidelity quantum state engineering based on two different optical parametric oscillators.

The presented technique enables a donation of quantum states that are important resources for a variety of information protocols. Significantly, or procedure based on optical parametric sate or oio makes possible to obtain a very low and mixture of vacuum ID 80 states and the emission into well controlled special mold sent to the oio cavity. This feature facilitates the use of these stats in subsequent protocols where they may need to interfere with other optical resources, for instance, in optical GA implementations or in more complex content.

Set engineering To perform this procedure, build a semi monolithic linear cavity for improved mechanical stability and reduced int cavity losses is include a KTP crystal and an input mirror that is directly coated on one face of the nonlinear crystal while the other face is anti reflection coated. Choose an input coupler reflection of 95%for the pump at 532 nanometers and high reflection for the signal and idler at 1064 nanometers. Inversely choose the output coupler to be highly reflective for the pump and of transmittance.

T equals 10%for the infrared. The free spectral range of the optical parametric oscillator is equal to 4.3 gigahertz and the bandwidth is around 60 megahertz. Use a continuous wave frequency doubled neodymium YAG laser as a laser source pump the OPO at 532 nanometers a, achieve the mode matching between the pump and the cavity mode.

Make the cavity triply resonant by adjusting the temperature of the crystal and the frequency of the laser. Check the transmission peaks for the infrared and green light on a scope for this purpose. A weak infrared light is also injected into the OPO lock.

The OPO cavity length on the pump resonance by the pound DRE Hall technique. For this purpose, apply an electro optic modulation to the pump and detect the light back reflected from the cavity with an optical isolator on a polarizing beam splitter. Separate the signal and idler fields.

One corresponds to the heralding mode while the other one is the heralded state that will be detected by the homo dyne detection. Guide the heralding mode towards the single photon detector. Filter the heralding mode to remove the frequency non degenerate modes due to the OPO cavity.

First, use an inferential filter with a bandwidth of 0.5 nanometers. Add a homemade linear Fabry Perot cavity with a free spectral range of 330 gigahertz and a bandwidth of 300 megahertz. The cavity bandwidth is chosen to be larger than that of the OPO and the free spectral range to be larger than the frequency window of the inferential filter.

Achieve at least an overall 25 decibel rejection of the non degenerate modes. After stabilizing the path as detailed in the text protocol, detect the filtered heralding mode by a single photon detector during the measurement period. A superconducting single photon detector is used to limit the amount of dark noise, which otherwise would degrade.

The fidelity of the conditional state. Detect the heralded state with a balanced homo dine detection composed of a 50 50 beam splitter where the field to characterize and a strong continuous wave local oscillator are brought to interfere as well as a pair of high quantum efficiency in gas photodiodes. In order to align the detection, inject a bright auxiliary beam at 1064 nanometers into the OPO cavity and mode.

Match this with the local oscillator mode. Achieve a fringe visibility close to unity. Any mode mismatch quadratic translates into detection losses.

Check the homo detection properties with a local oscillator power of six milliwatts. The shot noise limit is flat up to 50 megahertz. It is more than 20 decibels above the electronic noise at low analysis frequency, and 16 decibels above at the analysis frequency of 50 megahertz.

This distance is a critical parameter as it translates into losses in the detection. For every detection event from the single photon detector, record the ho moddy photo current using an oscilloscope with a sampling rate of five giga samples per second. During 100 nanoseconds.

Sweep the local oscillator phase with a PZT mounted mirror during the measurement. After filtering each recorded segment, accumulate measurements and post-process the data with a maximum likelihood algorithm. This procedure enables reconstruction of the density matrix of the heralded state and the corresponding Wagner function.

The tomographic reconstruction of the heralded state is visualized through the diagonal elements of the reconstructed density matrix and the corresponding Wagner function without any loss corrections. The heralded state exhibits a single photon component as high as 78%By taking into account the overall detection losses, the state reaches a fidelity of 91%with a single photon state. The two photon component, which results from multi photon pairs created by the down conversion process is limited to 3%A similar procedure can be applied with a type one appeal, which is a sort of single mode squeeze light.

By reflecting a small fraction of the squeeze vacuum states. With a beam splitter, one can subtract a single photon, which errors the preparation of a your kitten. On the other mode, the conditioning mode needs the same frequency filtering as explained In the other experiments, the arrow that states is characterized in the same way The conditional preparation technique presented here is always an interplay between the initial lateral source and the measurement performed by the he loading detector.

These two components strongly influence the quantum properties of the generated state due to the C crystals, unity, escape, efficiency of the OPOs and the very low duck noise of our superconducting detector for heavy loading. The method presented here enables the reliable generation of nongo states with very high fidelity, mainly limited by the losses in the detection. Don't forget that working with lasers can be extremely hazardous, and precautions such as wearing laser safety goggles should always be taken while performing this procedure.