In this paper we examine the N-photon absorption properties of "N00N" states, a subclass of path entangled number states. We consider two cases. The first involves the N-photon absorption properties of the ideal N00N state, one that does not include spectral information. We study how the N-photon absorption probability of this state scales with N. We compare this to the absorption probability of various other states. The second case is that of two-photon absorption for an N = 2 N00N state generated from a type II spontaneous down conversion event. In this situation we find that the absorption probability is both better than analogous coherent light (due to frequency entanglement) and highly dependent on the optical setup. We show that the poor production rates of quantum states of light may be partially mitigated by adjusting the spectral parameters to improve their two-photon absorption rates. This work has application to quantum imaging, particularly quantum lithography, where the N-photon absorbing process in the lithographic resist must be optimized for practical applications.
In this paper we examine the N-photon absorption properties of "N00N" states, a subclass of path entangled number states. We consider two cases. The first involves the N-photon absorption properties of the ideal N00N state, one that does not include spectral information. We study how the N-photon absorption probability of this state scales with N. We compare this to the absorption probability of various other states. The second case is that of two-photon absorption for an N = 2 N00N state generated from a type II spontaneous down conversion event. In this situation we find that the absorption probability is both better than analogous coherent light (due to frequency entanglement) and highly dependent on the optical setup. We show that the poor production rates of quantum states of light may be partially mitigated by adjusting the spectral parameters to improve their two-photon absorption rates. This work has application to quantum imaging, particularly quantum lithography, where the N-photon absorbing process in the lithographic resist must be optimized for practical applications.
In this paper we examine the N-photon absorption properties of maximally path-entangled number states (N00N states). We consider two cases. The first involves the N-photon absorption properties of the ideal N00N state, one that does not include spectral information. We study how the N-photon absorption probability of this state scales with N, confirming results presented by others in a previous paper by a different method. We compare this to the absorption probability of various other states. The second case is that of two-photon absorption for an N=2N00N state generated from a type-II spontaneous down-conversion event. In this situation we find that the absorption probability is both better than analogous coherent light (due to frequency entanglement) and highly dependent on the optical setup. We show that the poor production rates of quantum states of light may be partially mitigated by adjusting the spectral parameters to improve their two-photon absorption rates. This work has application to quantum imaging, particularly quantum lithography, where the N-photon absorbing process in the lithographic resist must be optimized for practical applications.
Abstract We study the two-photon absorption properties of frequency-entangled N00N states produced in a Hong-Ou-Mandel interferometer using type-I degenerate photon pairs, generated via spontaneous parametric down-conversion. By comparing our results with N00N states with no frequency entanglement, we demonstrate enhanced two-photon absorption due to frequency entanglement. We also derive an analytic expression for the enhancement factor which is found to be greater than one for all finite values of the ratio of the bandwidth of the pump to the bandwidth of the detected photons. We have also found suppression and enhancement in the two-photon absorption probabilities for specific time delays applied to the N00N states.
Recent results in deeply subwavelength thickness films demonstrate coherent control and logical gate operations with both classical and single-photon light sources. However, quantum processing and devices typically involve more than one photon and nontrivial input quantum states. Here we experimentally investigate two-photon N00N state coherent absorption in a multilayer graphene film. Depending on the N00N state input phase, it is possible to selectively choose between single- or two-photon absorption of the input state in the graphene film. These results demonstrate that coherent absorption in the quantum regime exhibits unique features, opening up applications in multiphoton spectroscopy and imaging.
Over a century after the modern prediction of the existence of individual particles of light by Albert Einstein, a reliable source of this simple quantum state of one photon does not exist. While common light sources such as a light bulb, LED, or laser can produce a pulse of light with an average of one photon, there is (currently) no way of knowing the number of photons in that pulse without first absorbing (and thereby destroying) them. Spontaneous parametric down-conversion, a process in which one high-energy photon splits into two lower-energy photons, allows us to prepare a single-photon state by detecting one of the photons, which then heralds the existence of its twin. This process has been the workhorse of quantum optics, allowing demonstrations of a myriad of quantum processes and protocols, such as entanglement, cryptography, superdense coding, teleportation, and simple quantum computing demonstrations. All of these processes would benefit from better engineering of the underlying down-conversion process, but despite significant effort (both theoretical and experimental), optimization of this process is ongoing. The focus of this work is to optimize certain aspects of a down-conversion source, and then use this tool in novel experiments not otherwise feasible. Specifically, the goal is to optimize the heralding efficiency of the down-conversion photons, i.e., the probability that if one photon is detected, the other photon is also detected. This source is then applied to two experiments (a single-photon source, and a quantum cryptography implementation), and the detailed theory of an additional application (a source of Fock states and path-entangled states, called N00N states) is discussed, along with some other possible applications.
Multiple photon absorption processes typically have a nonlinear dependence on the amplitude of the incident optical field. On the other hand, quantum technologies rely on single photon events. It has therefore been of great technical difficulty to achieve nonlinear devices using single photons. This is due to the small cross-section of absorption in room temperature devices, with multi-photon absorption events occurring with extremely low probability. The lack of access to nonlinear processes severely inhibits the use of optics for a large number of applications surrounding quantum technologies. We demonstrate experimentally that by exploiting a coherent absorption mechanism for N=2 N00N states, outlined theoretically by Jeffers in 2000 [1] and experimentally explored by Roger et. al. in 2016 [2], that it is possible to determine and enhance the number of two photon states that are absorbed. Here a 50% absorbing metasurface is placed inside a Sagnac interferometer into which we inject a N00N state. We show that by tuning the phase φ of the input state, |2,0〉 + exp(-ί2φ) |0,2〉, we can selectively tune the output state. For an input phase of φ = π/2 or 3π/2 we find that a single photon is absorbed with 100% probability. However, when we tune the input phase to φ = 0 or π we see that either 0 or 2 photons are absorbed with equal probability. We have developed a theoretical model that, with no free parameters, fits the experimentally measured two-photon contribution and finds the maximum contribution of |0,0) (0,0| to the output state to be 40.5%.
We optimize two-mode entangled number states of light in the presence of loss in order to maximize the extraction of the available phase information in an interferometer. Our approach optimizes over the entire available input Hilbert space with no constraints, other than fixed total initial photon number. We optimize to maximize the Fisher information, which is equivalent to minimizing the phase uncertainty. We find that in the limit of zero loss, the optimal state is the maximally path-entangled (so-called N00N) state, for small loss, the optimal state gradually deviates from the N00N state, and in the limit of large loss, the optimal state converges to a generalized two-mode coherent state, with a finite total number of photons. The results provide a general protocol for optimizing the performance of a quantum optical interferometer in the presence of photon loss, with applications to quantum imaging, metrology, sensing, and information processing.