Quantum Entanglement of High Angular Momenta (original) (raw)
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Precise quantum tomography of photon pairs with entangled orbital angular momentum
New Journal of Physics, 2009
We report a high fidelity tomographic reconstruction of the quantum state of photon pairs generated by parametric down-conversion with orbital angular momentum (OAM) entanglement. Our tomography method allows us to estimate an upper and lower bound for the entanglement between the downconverted photons. We investigate the two-dimensional state subspace defined by the OAM states ±`and superpositions thereof, with`= 1, 2, . . . , 30. We find that the reconstructed density matrix, even for OAMs up to around`= 20, is close to that of a maximally entangled Bell state with a fidelity in the range between F = 0.979 and F = 0.814. This demonstrates that, although the single count-rate diminishes with increasing`, entanglement persists in a large dimensional state space.
Orbital angular momentum analysis of high-dimensional entanglement
Physical Review A, 2007
We describe a simple experiment that is ideally suited to analyze the high-dimensional entanglement contained in the orbital angular momenta ͑OAM͒ of entangled photon pairs. For this purpose we use a two-photon interferometer with a built-in image rotator and measure the two-photon visibility versus rotation angle. Mode selection with apertures allows one to tune the dimensionality of the entanglement; mode selection with spiral phase plates and fibers allows detection of a single OAM mode. The experiment is analyzed in two different ways: either via the continuous two-photon amplitude function or via a discrete modal ͑Schmidt͒ decomposition of this function. The latter approach proves to be very fruitful, as it provides a complete characterization of the OAM entanglement.
Quantum Information Transfer from Spin to Orbital Angular Momentum of Photons
Physical Review Letters, 2009
The optical "spin-orbit" coupling occurring in a suitably patterned nonuniform birefringent plate known as 'q-plate' allows entangling the polarization of a single photon with its orbital angular momentum (OAM). This process, in turn, can be exploited for building a bidirectional "spin-OAM interface", capable of transposing the quantum information from the spin to the OAM degree of freedom of photons and vice versa. Here, we experimentally demonstrate this process by singlephoton quantum tomographic analysis. Moreover, we show that two-photon quantum correlations such as those resulting from coalescence interference can be successfully transferred into the OAM degree of freedom.
Increasing the dimension in high-dimensional two-photon orbital angular momentum entanglement
Physical Review A, 2012
Any practical experiment utilising the innate D-dimensional entanglement of the orbital angular momentum (OAM) state space of photons is subject to the modal capacity of the detection system. We show that given such a constraint, the number of measured, entangled OAM modes in photon pairs generated by spontaneous parametric down-conversion (SPDC) can be maximised by tuning the phase-matching conditions in the SPDC process. We demonstrate a factor of 2 increase on the half-width of the OAM-correlation spectrum, from 10 to 20, the latter implying ≈ 50-dimensional two-photon OAM entanglement. Exploiting correlations in the conjugate variable, angular position, we measure concurrence values 0.96 and 0.90 for two phase-matching conditions, indicating bipartite, D-dimensional entanglement where D is tuneable.
High-dimensional entanglement with orbital-angular-momentum states of light
We engineer high-dimensional orbital-angular-momentum entanglement of photon pairs that emerge from a parametric down-conversion source. By means of two angular state analysers, in essence composed of a rotatable multi-sector phase plate and a single-mode fibre, we perform selective projective measurements that maximize the Shannon dimensionality D of the measured entanglement. The multi-sector phase plates have a binary phase profile along the azimuthal coordinate, and the arc sector sizes are optimized so as to maximize D.We find that the maximum dimensionality increases linearly with the number of sectors N. The potential of our method is illustrated with an experiment for N = 4, yielding D = 16.5.
Physical Review Letters, 2009
Three-dimensional entanglement of orbital angular momentum states of an atomic qutrit and a single photon qutrit has been observed. Their full state was reconstructed using quantum state tomography. The fidelity to the maximally entangled state of Schmidt rank 3 exceeds the threshold 2/3. This result confirms that the density matrix cannot be decomposed into ensemble of pure states of Schmidt rank 1 or 2. That is, the Schmidt number of the density matrix must be equal to or greater than 3.
Journal of Modern Optics, 2002
We calculate the anticipated correlation between measurements of the orbital angular momentum of the signal and idler beams for parametric down-conversion. These calculations apply to the experiments where the orbital angular momentum state is measured by the use of computer-generated holograms. Displacement of these holograms with respect to the beam axis allows the measurement of superpositions of Laguerre±Gaussian modes. The correlations between such superposition modes of the signal and idler beams show their entanglement and could be used for Bell-type tests of nonlocality. Over the past 20 years many experiments have been performed to study polarization entanglement of photon pairs. The experiments of Aspect and coworkers [1] in the early 1980s are generally regarded as having provided the ®rst experimental support for nonlocal interpretations of quantum mechanics. Since that time, other experiments on photon pairs have successfully shown entanglement in their polarization states [2], their arrival times [3, 4] and their transverse position [5]. In addition to investigating the interpretation of quantum mechanics, entanglement also plays important roles in quantum cryptography [6] and teleportation [7]. Recently, Mair et al. [8] reported the ®rst experiments to investigate the entanglement of the orbital angular momentum of photon pairs using computergenerated holograms to measure the orbital angular momentum of individual photons. While the polarization of light, related to the spin angular momentum, can be characterized by two orthogonal states, the orbital angular momentum is higher dimensional [9]. The multi-dimensional entanglement of orbital angular momentum states could ®nd interesting applications in quantum cryptography and communication. This paper seeks to apply our recently derived theoretical treatment [10] of the correlation between orbital angular momentum states to experiments of their type. We also suggest more detailed experiments to observe the entanglement of the
Quantum entanglement of angular momentum states with quantum numbers up to 10,010
Proceedings of the National Academy of Sciences
Photons with a twisted phase front carry a quantized amount of orbital angular momentum (OAM) and have become important in various fields of optics, such as quantum and classical information science or optical tweezers. Because no upper limit on the OAM content per photon is known, they are also interesting systems to experimentally challenge quantum mechanical prediction for high quantum numbers. Here, we take advantage of a recently developed technique to imprint unprecedented high values of OAM, namely spiral phase mirrors, to generate photons with more than 10,000 quanta of OAM. Moreover, we demonstrate quantum entanglement between these large OAM quanta of one photon and the polarization of its partner photon. To our knowledge, this corresponds to entanglement with the largest quantum number that has been demonstrated in an experiment. The results may also open novel ways to couple single photons to massive objects, enhance angular resolution, and highlight OAM as a promising w...