In sensors, the highest precision in measurements is given by vacuum fluctuations of quantum mechanics, resulting in a shot noise limit. In a Mach-Zenhder interferometer (MZI), the intensity measurement is correlated with the phase, and thus, the precision measurement (Δn) is coupled with the phase resolution (Δφ) by the Heisenberg uncertainty principle. Quantum metrology offers a different solution to this precision measurement using nonclassical light such as squeezed light or higher-order entangled-photon pairs, resulting in a smaller Δφ and sub-shot noise limit. Here, we propose another method for the high precision measurement overcoming the diffraction limit in classical physics, where the smaller Δφ is achieved by phase quantization in a coupled interferometric system of coherence de Broglie waves. For a potential application of the proposed method, a quantum ring laser gyroscope is presented as a quantum version of the conventional ring laser gyroscope used for inertial navigation and geodesy.
In sensors, the highest precision in measurements is given by vacuum fluctuations of quantum mechanics, resulting in a shot noise limit. In a Mach-Zenhder interferometer (MZI), the intensity measurement is correlated with the phase, and thus, the precision measurement (Δn) is coupled with the phase resolution (Δφ) by the Heisenberg uncertainty principle. Quantum metrology offers a different solution to this precision measurement using nonclassical light such as squeezed light or higher-order entangled-photon pairs, resulting in a smaller Δφ and sub-shot noise limit. Here, we propose another method for the high precision measurement overcoming the diffraction limit in classical physics, where the smaller Δφ is achieved by phase quantization in a coupled interferometric system of coherence de Broglie waves. For a potential application of the proposed method, a quantum ring laser gyroscope is presented as a quantum version of the conventional ring laser gyroscope used for inertial navigation and geodesy.
In a Mach-Zenhder interferometer (MZI), the highest precision for a measurement error is given by vacuum fluctuations of quantum mechanics, resulting in a shot noise limit1,2,3,4,5. Because the intensity measurement in an MZI is correlated with the phase difference, the precision measurement (Δn) is coupled with the phase resolution (Δϕ) by the Heisenberg uncertainty principle. Quantum metrology offers a different solution to this precision measurement using nonclassical light such as squeezed light or higher-order entangled-photon pairs, resulting in a smaller Δϕ for the same Δn3,4,5,6,7,8. Here, we propose another method for the high precision measurement overcoming the Heisenberg photon-phase relation, where the smaller Δϕ is achieved by phase quantization in a coupled interferometric system via coherence de Broglie waves (CBWs)9,10. For a potential application of the proposed method, a quantum ring gyroscope is presented as a quantum version of the conventional ring laser gyroscope used for inertial navigation and geodesy11-13.
Quantum measurements have been intensively researched over decades due to quantum advantage of Heisenberg limit beating the standard quantum limit toward potential applications of quantum metrology. The kernel of quantum measurements is in the quantum correlation between bipartite photon pairs or squeezed light quenched by one parameter over corresponding noncommuting variable satisfying Heisenberg uncertainty principle. As a result, quantum measurements bring a quantum gain of the square root law in measurement sensitivity. Photonic de Broglie waves (PBW) have been the key feature of such a gain in quantum metrology especially for phase resolution enhancement beyond the classical limit of Rayleigh criterion or simply the diffraction limit. Due to extremely low efficiency of higher-order entangled photon pair generations such as a NOON state, however, the implementation of PBW for quantum metrology has been severely limited. Here, a completely different mechanism of quantum measurements is introduced for a new type of PBW and presented for its potential application of a modified Sagnac interferometer, where the resolution enhancement is several orders of magnitude higher than its classical counterpart.
Quantum techniques, developed in recent decades, provide new approaches to achieving high-precision measurements beyond the classical bounds. In this paper, we theoretically demonstrate a metrology method for improving the sensitivity of the interferometric optical gyroscope, robust against the loss, by using coherent-light stimulated two-mode squeezed beams as the light source. The detection protocol is based on a simple intensity measurement, and the quantum noise is far below the shot-noise limit. The enhancement factors for different coherent light fields are analyzed in detail. Additionally, the influence of loss during the propagation in the optical path is studied, and the conditions for achieving sub-shot-noise measurement sensitivity are obtained. We also find that the phase sensitivity of the proposed gyroscope scheme becomes closer to the quantum Cramér-Rao bound with increasing of the photon number of the coherent beams.
Quantum measurements have been intensively researched over decades due to quantum advantage of Heisenberg limit beating the standard quantum limit toward potential applications of quantum metrology. The kernel of quantum measurements is in the quantum correlation between bipartite photon pairs or squeezed light quenched by one parameter over corresponding noncommuting variable satisfying Heisenberg uncertainty principle. As a result, quantum measurements bring a quantum gain of the square root law in measurement sensitivity. Photonic de Broglie waves (PBW) have been the key feature of such a gain in quantum metrology especially for phase resolution enhancement beyond the classical limit of Rayleigh criterion or simply the diffraction limit. Due to extremely low efficiency of higher-order entangled photon pair generations such as a NOON state, however, the implementation of PBW for quantum metrology has been severely limited. Here, a completely different mechanism of quantum measurements is introduced for a new type of PBW and presented for its potential application of a modified Sagnac interferometer, where the resolution enhancement is several orders of magnitude higher than its classical counterpart.
Interferometer-based precision measurements have been intensively studied for sensing and metrology over the past half century. In classical optics, the resolution and phase sensitivity of an optical signal are confined by diffraction limit and shot-noise limit (SNL), respectively. Highly entangled photon pairs, i.e., N00N states have been adapted to overcome SNL in quantum sensing over the last two decades. Recently, coherent light-excited quantum sensing has also been proposed and demonstrated for macroscopic quantum sensing to overcome the limited N scalability in N00N-based quantum sensing. Here, a Sagnac interferometer-based superresolution is proposed to solve environmental noises inevitable in an interferometer. Furthermore, a spatial light modulator takes over the role of phase-controlled quantum erasers to solve the linear optics-based complexity issue in the coherently-excited superresolution. Thus, the proposed Sagnac superresolution can beat the state-of-the-art ring laser gyroscope applied for inertial navigation and geodesy.
According to the Heisenberg uncertainty principle, the precision of any physical quantity measurement is limited by quantum fluctuation in general, which leads to the so-called standard quantum limit (SQL). The SQL can be beaten by using squeezed light, hence enhancing the measurement accuracy. Squeezed light is a typical nonclassical light, it exhibits reduced noise in one quadrature component. Since Caves proposed the scheme of phase measurement enhancement with squeezing, squeezed light has been used to enhance measurement precision in many areas. This review focuses on the following four kinds of precision measurements based on squeezed light: the measurements of relative phase, small lateral displacement and tilt, magnetic field, and clock synchronization. For all of these measurements, vacuum squeezing has been used to enhance measurement precision, while the types of squeezing (squeezing angle, transverse mode, polarization etc.) are different. For phase measurement, quadrature squeezing is injected into the conventionally unused input port of Mach-Zehnder interferometer (MZI) or Michelson interferometer (MI). For displacement or tilt measurement, a vacuum squeezing beam of a special transverse mode is coupled into an intense coherent beam, yielding a spatial-squeezed light whose transverse position or tilt angle noise is lower than that of a classical light beam. Based on the Faraday effect of polarization rotation, the magnetic field can be detected precisely. The precision can be increased further by using the polarization squeezing. The polarization squeezing can be generated by coupling two orthogonal polarized beams together, a coherent beam and a vacuum squeezed beam. Various polarization squeezing can be illustrated on the Poincaré sphere. Finally, in the clock synchronization based on the optical frequency comb, squeezed light can be used to enhance the time measurement precision. A theoretical scheme with multimode squeezing of supermode (a kind of mode describing the frequency mode of a pulse laser beam) is introduced. The squeezing has extensively been applied into the quantum precision measurements such as gravitational wave detection as well as biological measurement and will play a more important role in the near future.