Abstract This paper experimentally and theoretically investigates improving interaction free measurement (IFM) efficiency using a chain of multiple interferometers with transmissive beam splitters of reflectivity less than 50%. The object measured with IFM is present or absent from one of the interferometer paths depending on the polarization of the incident light. The ability to effectively move an object in and out of the system without physically moving it makes implementing a multiple chain interferometer more practical. It also allows verifying the desired interferometer phase while simultaneously making the IFM measurement. A recursive phase model of a chain of interferometers is presented which accounts for both losses and arbitrary phase differences between each pair of arms in the chain. The recursive model predicts the photodiode power and is experimentally validated for a chain of interferometers of lengths one and two.
Abstract This paper experimentally and theoretically investigates improving interaction free measurement (IFM) efficiency using a chain of multiple interferometers with transmissive beam splitters of reflectivity less than 50%. The object measured with IFM is present or absent from one of the interferometer paths depending on the polarization of the incident light. The ability to effectively move an object in and out of the system without physically moving it makes implementing a multiple chain interferometer more practical. It also allows verifying the desired interferometer phase while simultaneously making the IFM measurement. A recursive phase model of a chain of interferometers is presented which accounts for both losses and arbitrary phase differences between each pair of arms in the chain. The recursive model predicts the photodiode power and is experimentally validated for a chain of interferometers of lengths one and two.
Recently, it has been pointed out that it is possible to make a quantum-mechanical interaction-free measurement (IFM), in which the existence of an object in a given region of space may be determined seemingly without interacting with it.1,2 In the embodiment first proposed by Elitzur and Vaidman,3 a standard Michelson interferometer is aligned so that incident single photons (obtained in our experiment by using parametric downconversion; see Fig. 1) must exit by the same port in which they entered, in the absence of any object within the interferometer. The presence of an object (e.g., the mirror leading to detector DB) in one of the arms completely changes the possible outcomes because the constructive interference is interrupted. Now it is possible that the photon will exit from the other exit port, to detector DIfm. By detecting the photon in this case, one can claim with certainty that an object was within the interferometer, even though the photon could not have interacted with it. If the beam splitter has a very low reflectivity, then the fraction of IFMs approaches 1/2.
Abstract The presence of an object can be detected without the absorption of photons in an interaction-free measurement (IFM) system based on the Zeno effect in chained Mach–Zehnder interferometers (MZIs). In this paper, we propose a scheme with an unbalanced MZI to perform the transmission of two frequency components of input light simultaneously. The two components are separated at two output ports of the MZI, achieving a high probability of asserting the absence of the object. The two final outputs of the MZI can also be extended to perform special information processing via IFM. As a result, this proposal contributes to the improvement of efficiency in interaction-free measurements with a very small number of interferometers for potential practical implementations of quantum information technology.
Semitransparent mirrors are standard elements in light optics for splitting light beams or creating two versions of the same image. Such mirrors do not exist in electron optics, although they could be beneficial in existing techniques such as electron interferometry and holography and could enable alternative electron imaging and spectroscopy techniques. We propose a design for an electron beam splitter using the concept of quantum interaction-free measurement (IFM). The design combines an electron resonator with a weak phase grating. Fast switching gates allow electrons to enter and exit the resonator. While in the resonator, the phase grating transfers intensity from the direct beam into one of the weakly diffracted beams at each pass. To make the beam splitter an efficient two-port splitter, the intensity in all other diffracted beams is blocked by an aperture. The IFM principle minimizes the loss of total intensity by this aperture. We use a scattering matrix method to analyze the performance of the beam splitter, including the effects of inelastic scattering in the phase grating. This design can be generalized to beam splitters for not only electrons, but also photons, neutrons, atoms, and other quantum mechanical systems.
"Interaction-free measurements" (IFM) originate from the latest quantum interferometric technologies. The latest research of quantum optics demonstrates, by using the complementary wavelike and particlelike natures of photons, it is possible to make interaction-free measurements by which the presence of an object can be determined with no photons being absorbed. The paper introduces the concept of "Interaction-free Measurement" (IFM), the original Elitzur-Vaidman scheme, the "High Efficiency Interaction-free Measurement", the application of quantum Zeno effect and the improved scheme proposed by Kwiat et al. The EV scheme is implemented in a Mach-Zehnder interferometer. Theoretically this paper also draws a conclusion in IFM feasibility by analyzing the wave functions of photon at various locations in the interferometer.
An interaction-free measurement system with a polarization-based Mach-Zehnder interferometer structure is analyzed for semitransparent objects. Here, it is shown that the interaction-free measurement of such objects with 100% detection efficiency is possible in principle if the system loss is negligible. The influence of two system imperfections, the system loss and the low quantum efficiency of the photon detectors, on the interaction-free measurement is also analyzed. Although the two system imperfections limit the maximal detection efficiency that can be achievable, the quantum efficiency of the photon detectors is less important when the system loss becomes small.
In this paper, we consider interaction-free measurement (IFM) with imperfect interaction. In the IFM proposed by Kwiat et al., we assume that interaction between an absorbing object and a probe photon is imperfect, so that the photon is absorbed with probability 1-\\eta (0\\leq\\eta\\leq 1) and it passes by the object without being absorbed with probability \\eta when it approaches close to the object. We derive the success probability P that we can find the object without the photon absorbed under the imperfect interaction as a power series in 1/N, and show the following result: Even if the interaction between the object and the photon is imperfect, we can let the success probability P of the IFM get close to unity arbitrarily by making the reflectivity of the beam splitter larger and increasing the number of the beam splitters. Moreover, we obtain an approximating equation of P from the derived power series in 1/N.