Quantum entanglement of angular momentum states with quantum numbers up to 10,010

Abstract

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 way to increase the information capacity of a single photon.quantum entanglement | orbital angular momentum | photonic spatial modes | quantum foundations P hotonic systems are an excellent platform to test the foundations of quantum physics (1). Photonic technologies used to generate, manipulate, and measure one of its key features, quantum entanglement, have matured to an unprecedented level. In various experiments the limit of extending quantum mechanical predictions to the macroscopic regimes have been investigated by increasing the distance between the entangled photons (2, 3), the numbers of involved photonic systems (4), or the dimensionality of the entanglement (5). In another approach, the property of orbital angular momentum (OAM), which is related to the helical phase structure of the photons (6) in the paraxial regime and can be used to rotate particles around the optical axis (7), has been explored in quantum entanglement experiments (8). Interestingly, according to quantum theory this angular momentum can, in principle, be arbitrarily large even for entangled quantum states of single photons. If large enough, this angular momentum can conceivably be transferred to macroscopic particles, which could open novel ways of investigating light-matter interactions. Additionally, large OAM quanta of photonic quantum states are an interesting property to investigate the fundamental question regarding the existence of a quantum-classical transition. It is still believed by many people and often cited in textbooks in connection to Bohr's correspondence principle (see e.g., ref. 9) that the quantum-classical transition has to occur when the quantum number of the investigated state becomes very large. However, in the opinion of the authors and many others, such a simple relation is not correct (e.g., see also ref. 10). Therefore, generating quantum states with large quantum numbers (e.g., high OAM values) are important experimental tests to challenge and clarify these fundamental questions. A recent experiment toward these directions d...

Naked eye picometer resolution in a Michelson interferometer using conjugated twisted beams

“…They plotted the intensity distribution and found a daisy flower interference pattern like the one found here. This is similar to what is observed in entanglement experiments [23,24]. This is evidenced on Fig.…”

“…The typical size of a LG beam varies as r max = w 0 ℓ/2 [28]. For ℓ = 300, this leads to r max = 12w 0 which is reasonable, whereas for ℓ = 10000 [24] this leads to r max = 100w 0 . Larger mirrors (of the order of 1 m) have then to be used.…”

Generating High‐Charge Optical Vortices Directly from Laser Up to 288th Order

“…In a Michelson interferometer‐based displacement measurement system using a vortex beam, the measurement resolution will reach 10 −16 m if the topological charge is 300 . Moreover, high‐charge optical vortices may provide an ideal platform for experimentally testing fundamental quantum physics such as clarifying whether there exist macroscopic entanglement and quantum‐classical transition when the quantum number is very large . Therefore, it is important to generate high‐charge optical vortices for the development of not only technical science but also fundamental science.…”

“…For the generation of high‐charge optical vortices, the traditional method is to modulate the Gaussian beam outside the laser by a spatial light modulator (SLM) or a spiral phase plate (SPP) . However, optical vortices generated with the traditional method present an intrinsic transmission instability due to imperfections of phase element processing .…”

Vortex-free laser beam with an orbital angular momentum

“…This mirror can generate optical vortices with the topological charge of 1020. Using a spiral aluminum mirror with a diameter of about 50 mm, entangled photons for the wavelength of 810 nm were detected in [12]. The photons were entangled by the OAM and polarization, and what is more, the quantum OAM of photons was equal to ±10010.…”