Characterizing and Tailoring Spatial Correlations in Multimode Parametric Down-Conversion

Quick Quantum Steering: Overcoming Loss and Noise with Qudits

“…To experimentally demonstrate noise-robust EPR steering with the fair-sampling loophole closed, we use pairs of photons entangled in their discrete transverse positionmomentum degree of freedom, also known as pixel entanglement [54,55]. As shown in Fig.…”

“…This enables Alice to maximize the detection efficiency of her SLM and channel. Bob's measurement basis design is informed by prior knowledge of the two-photon joint-transversemomentum amplitude (JTMA) [54], which allows him to tailor his pixel mask in order to optimize the resultant onesided heralding efficiency in the experiment η exp (see Appendix B). The choice of the phase-only pixel basis gives the added advantage that projective measurements in mutually unbiased bases provide the highest possible SLM heralding efficiency, since they do not require any amplitude modulation in their holograms [56].…”

“…to be close to a maximally entangled state in dimension d owing to the knowledge of the JTMA of the generated twophoton state, which maximizes its entanglement of formation [54,55]. In our experiment, we utilize the crosstalk between individual pixels as a reliable measure of the system noise parameter [p exp ; see Eq.…”

Entangled ripples and twists of light: radial and azimuthal Laguerre–Gaussian mode entanglement

“…The IFTs in our system effectively magnify the back-propagated collection modes at the SLM planes by a factor of 3.3 to mitigate the effects of the SMF Gaussian component. In addition, the IFTs allow us to tailor the collection modes to the size of the quantum spiral bandwidth of the generated state [53], as determined by the extent of the JTMA [46,50]. Note also that increasing the size of the collection modes at the SLMs is equivalent to reducing the size of the collection mode waists w s,i at the crystal, which increases the ratio γ exp to a value of 5.26, in turn reducing radial mode cross-talk between signal and idler photons [34].…”

“…where Φ(k s , k i ) is the measured joint transverse momentum amplitude (JTMA) of the biphoton state [50]. The JTMA is a function determined by the spatial profile of the pump, the phase matching conditions in SPDC [34,[50][51][52], as well as the collection optics. The JTMA describes the measured correlations in the transverse-momentum degree-of-freedom of the generated photons.…”