Abstract Quantum sensing and metrology have been intensively studied over the last several decades to surpass the fundamental shot-noise limit of classical systems and approach the Heisenberg limit. However, implementation of N00N-state-based quantum sensing has been severely constrained by the limited order N , intrinsically imperfect fringe visibility, and vulnerability to photon loss. Recently, the coherence de Broglie wavelength (CBW) has been proposed as an alternative method for achieving superresolution in a coherently coupled interferometer architecture, whose characteristics resemble those of the photonic de Broglie wavelength (PBW) used in quantum sensing. Here, we experimentally demonstrate scalable CBW superresolution up to N =3, with near-perfect fringe visibility that is invariant to photon loss. The observed CBWs have the potential to enable a superresolution sensing platform even if it remains within the shot-noise limit.
Abstract Quantum sensing and metrology have been intensively studied over the last several decades to surpass the fundamental shot-noise limit of classical systems and approach the Heisenberg limit. However, implementation of N00N-state-based quantum sensing has been severely constrained by the limited order N , intrinsically imperfect fringe visibility, and vulnerability to photon loss. Recently, the coherence de Broglie wavelength (CBW) has been proposed as an alternative method for achieving superresolution in a coherently coupled interferometer architecture, whose characteristics resemble those of the photonic de Broglie wavelength (PBW) used in quantum sensing. Here, we experimentally demonstrate scalable CBW superresolution up to N =3, with near-perfect fringe visibility that is invariant to photon loss. The observed CBWs have the potential to enable a superresolution sensing platform even if it remains within the shot-noise limit.
Quantum sensing and metrology have been extensively investigated over the past several decades to surpass the classical shot noise limit and approach the Heisenberg limit. The hallmark of N00N state based quantum sensing is superresolution, characterized by the interference fringe pattern (1+cosNphi). However, practical implementations are severely constrained by the achievable photon number N, reduced fringe visibility, and vulnerability to photon loss. Recently, several coherence-based approaches without using N00N states have been explored as alternative routes to superresolution. Among them, the coherence de Broglie wavelength (CBW) approach is fully compatible with coherence optics. Here, we experimentally demonstrate CBW based superresolution up to N=3. In contrast to N00N state based schemes, the observed CBW fringes exhibit near unity visibility that is essentially independent of N and remain robust against photon loss. Although CBW does not attain the Heisenberg limited phase sensitivity, its phase sensitivity exhibits an N fold enhancement over conventional classical interferometric approaches. These results suggest that CBW provides a practical and scalable platform for superresolution based sensing and metrology.
A quantum wavemetry scheme based on the coherence de Broglie wavelength (CBW) is proposed using an M coupled Mach Zehnder interferometer (MZI) architecture to achieve superresolution sensing and metrology. Although CBW does not attain the Heisenberg limit, it circumvents the key practical limitations of N00N state based quantum sensing, including restricted photon number N, reduced fringe visibility, and strong susceptibility to photon loss. The CBW approach enables loss tolerant operation with arbitrarily large M, while maintaining near unity fringe visibility. Fully compatible with coherence optics, the CBW scheme can be directly integrated into conventional wavemetry systems, providing both superresolution and enhanced sensitivity. A proof of principle experiment demonstrating CBW based superresolution is implemented using a Sagnac integrated round trip MZI structure for M=2, validating the feasibility of the proposed quantum wavemetry design.
Abstract Quantum sensing has drawn considerable attention as a means to overcome the fundamental limitations in classical sensing. In practice, however, quantum sensing has been strongly constrained by the photon loss, the achievable photon number N in N00N states, and by a finite squeezing level in squeezed states. These limitations are particularly critical to photon-loss-sensitive applications such as LiDAR as well as to general sensing platforms that require large effective N, such as ring-laser gyroscopes. Recently, fundamentally different sensing platforms have been reported to overcome both classical and quantum constraints in a practical regime. One such approach exploits the coherence de Broglie wavelength (CBW) realized in an anti-symmetrically coupled Mach-Zehnder interferometer (MZI) architecture. Here, a pure quantum mechanical analysis of the CBW is presented for a loss-free sensing mechanism of superresolution with enhanced sensitivity. A proof-of-principle demonstration of CBW is also presented.
Quantum sensing exploits nonclassical states of light, including multiphoton entangled states and squeezed states, to achieve superresolution and/or super-sensitivity. However, its practical implementation is constrained by state-generation complexity, photon loss, and detection efficiency. Here, we present a quantum-operator analysis of coherence de Broglie wavelength (CBW) in an anti-symmetrically coupled Mach-Zehnder interferometer (MZI) architecture and clarify the origin of its superresolution and enhanced phase sensitivity. The two-mode SU(2) structure of the MZI, represented by Pauli operators, shows that successive basis-realigned transformations produce an Nth-order unitary U^N(phi), yielding N-fold phase accumulation (1+cosNphi). The quantum-operator description is particularly significant at the single-photon level, where even a single photon undergoes the Nth-order unitary evolution through its coherent evolution in the two-mode state space. This differs from entanglement-based quantum sensing based on photonic de Broglie wavelength interferometry, where N-fold phase accumulation is associated with an N-photon entangled state. The same SU(2) transformation also applies to coherent classical fields, establishing a classical-quantum correspondence of the CBW phase evolution. Fisher-information analysis further shows that the architecture-induced phase transformation yields an order-dependent enhancement of phase sensitivity without increasing the photon number or statistical sampling. CBW therefore provides an architecture-controlled route to high-order interferometric superresolution, accompanied by enhanced phase sensitivity, with potential applications to fringe-counting wavemetry and Fourier-transform-based sensing.
Photonic de Broglie waves (PBWs) via two-mode entangled photon pair interactions on a beam splitter show a pure quantum feature which cannot be obtained by classical means1-4. Although PBWs have been intensively studied for quantum metrology5-13 and quantum sensing14-25 over the last several decades, their implementation has been limited due to difficulties of high-order NOON state generation4. Recently a coherence version of PBWs, the so-called coherence de Broglie waves (CBWs), has been proposed in a pure classical regime of an asymmetrically coupled Mach-Zehnder interferometer (MZI)26. Unlike PBWs, the quantumness of CBWs originates from the cascaded quantum superposition of the coupled MZI. Here, the first CBWs observation is presented in a pure classical regime and discussed for its potential applications in coherence quantum metrology to overcome conventional PBWs limited by higher-order entangled photons. To understand the quantum superposition-based nonclassical features in CBWs, various violation tests are also performed, where asymmetrical phase coupling is the key parameter for CBWs.
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.