arXiv subjects

Zi-Mo Cheng

Publications and source records attributed to Zi-Mo Cheng.

11 recordsLinked to original sources

arXiv2025

Observation of High-Order Quantum Pancharatnam-Berry Phase with Structured Photons

When a quantum system evolves so that it returns to its initial state, it will acquire a geometric phase acting as a memory of the transformation of a physical system, which has been experimentally measured in a variety of physical systems. In optics, the most prominent example is the Pancharatnam-Berry (PB) phase. Recent technological advances in phase and polarization structure have led to the discovery of high-order PB phases with structured light fields. The study on the high-order PB phase is limited in the context of elementary quantum states of light, especially in the case of photon number states. Here, we experimentally investigate the differences of high-order PB phases between single-photon and N00N states. Our results show that the PB phase, like the dynamic phase, can also be doubled under two-photon states, which can greatly improve the phase sensitivity for greater $N$ in N00N states and high-order structured photons. This may show some implications for quantum precision measurement and quantum state engineering based on geometric phase.

quant-ph↗

arXiv2025

Postselection-Free Cavity-Enhanced Narrow-Band Orbital Angular Momentum Entangled Photon Source

Cavity-enhanced spontaneous parametric down-conversion (SPDC) provides a significant way to produce $\sim$10 MHz narrow-band photon pairs, which matches the bandwidth of photon for quantum memory. However, the output photon pairs from the cavity is not entangled and the postselection is required to create the entanglement outside the cavity, so the direct output of cavity-enhanced narrow-band entangled photon pairs is still an open challenge. Here we propose a solution that realizes the first postselection-free cavity-enhanced narrow-band entangled photon pairs. The entanglement is achieved in degree of freedom (DOF) of orbital angular momentum (OAM) by implementing an OAM-conservation SPDC process in an actively and precisely controlled cavity supporting degenerate high-order OAM modes. The measured linewidth for the two photons is 13.8 MHz and the measured fidelity is 0.969(3) for the directly generated OAM entangled two photons. We deterministically transfer the OAM entanglement to polarization one with almost no loss and obtain polarization entangled two photons with a fidelity of 0.948(2). Moreover, we produce narrow-band OAM-polarization hyperentangled photon pairs with a fidelity of 0.850(2) by establishing polarization entanglement with preservation of OAM entanglement, which is realized by interfering the two photons on a polarizing beam splitter (PBS) and post-selecting the events of one and only one photon in on each of the PBS port. Novel cavity may find applications in cavity-based light-matter interaction. Our results provide an efficient and promising approach to create narrow-band entangled photon sources for memory-based long-distance quantum communication and network.

quant-ph↗

arXiv2025

Two-particle quantum interference in a nonlinear optical medium: a witness of timelike indistinguishability

The Hong-Ou-Mandel effect is a paradigmatic quantum phenomenon demonstrating the interference of two indistinguishable photons that are linearly coupled at a 50:50 beam splitter. Here, we transpose such a two-particle quantum interference effect to the nonlinear regime, when two single photons are impinging on a parametric down-conversion crystal. Formally, this transposition amounts to exchanging space and time variables, giving rise to an unknown form of timelike quantum interference. The two-photon component of the output state is a superposition of the incident photons being either transmitted or reborn, that is, replaced by indistinguishable substitutes due to their interaction with the nonlinear crystal. We experimentally demonstrate the suppression of the probability of detecting precisely one photon pair when the amplification gain is tuned to 2, which arises from the destructive interference between the transmitted and reborn photon pairs. This heretofore unobserved quantum manifestation of indistinguishability in time pushes nonlinear quantum interference towards a new regime with multiple photons. Hence, composing this effect with larger linear optical circuits should provide a tool to generate multimode quantum non-Gaussian states, which are essential resources for photonic quantum computers.

quant-ph↗

arXiv2024

Heralded High-Dimensional Photon-Photon Quantum Gate

High-dimensional encoding of quantum information holds the potential to greatly increase the computational power of existing devices by enlarging the accessible state space for fixed register size and by reducing the number of required entangling gates. However, qudit-based quantum computation remains far less developed than conventional qubit-based approaches, in particular for photons, which represent natural multi-level information carriers that play a crucial role in the development of quantum networks. A major obstacle for realizing quantum gates between two individual photons is the restriction of direct interaction between photons in linear media. In particular, essential logic components for quantum operations such as native qudit-qudit entangling gates are still missing for optical quantum information processing. Here we address this challenge by presenting a protocol for realizing an entangling gate -- the controlled phase-flip (CPF) gate -- for two photonic qudits in arbitrary dimension. We experimentally demonstrate this protocol by realizing a four-dimensional qudit-qudit CPF gate, whose decomposition would require at least 13 two-qubit entangling gates. Our photonic qudits are encoded in orbital angular momentum (OAM) and we have developed a new active high-precision phase-locking technology to construct a high-dimensional OAM beam splitter that increases the stability of the CPF gate, resulting in a process fidelity within a range of $ [0.64 \pm 0.01, 0.82 \pm 0.01]$. Our experiment represents a significant advance for high-dimensional optical quantum information processing and has the potential for wider applications beyond optical system.

quant-ph↗

arXiv2023

Manipulating spatial structure of high-order quantum coherence with entangled photons

High-order quantum coherence reveals the statistical correlation of quantum particles. Manipulation of quantum coherence of light in temporal domain enables to produce single-photon source, which has become one of the most important quantum resources. High-order quantum coherence in spatial domain plays a crucial role in a variety of applications, such as quantum imaging, holography and microscopy. However, the active control of high-order spatial quantum coherence remains a challenging task. Here we predict theoretically and demonstrate experimentally the first active manipulation of high-order spatial quantum coherence by mapping the entanglement of spatially structured photons. Our results not only enable to inject new strength into current applications, but also provide new possibilities towards more wide applications of high-order quantum coherence.

quant-ph↗

arXiv2022

Hong-Ou-Mandel Interference between Two Hyper-Entangled Photons Enables Observation of Symmetric and Anti-Symmetric Particle Exchange Phases

Two-photon Hong-Ou-Mandel (HOM) interference is a fundamental quantum effect with no classical counterpart. The exiting researches on two-photon interference were mainly limited in one degree of freedom (DoF), hence it is still a challenge to realize the quantum interference in multiple DoFs. Here we demonstrate the HOM interference between two hyper-entangled photons in two DoFs of polarization and orbital angular momentum (OAM) for all the sixteen hyper-entangled Bell states. We observe hyper-entangled two-photon interference with bunching effect for ten symmetric states (nine Boson-Boson states, one Fermion-Fermion state) and anti-bunching effect for six anti-symmetric states (three Boson-Fermion states, three Fermion-Boson states). More interestingly, expanding the Hilbert space by introducing an extra DoF for two photons enables to transfer the unmeasurable external phase in the initial DoF to a measurable internal phase in the expanded two DoFs. We directly measured the symmetric exchange phases being $0.012 \pm 0.002$, $0.025 \pm 0.002$ and $0.027 \pm 0.002$ in radian for the three Boson states in OAM and the anti-symmetric exchange phase being $0.991 \pi \pm 0.002$ in radian for the other Fermion state, as theoretical predictions. Our work may not only pave the way for more wide applications of quantum interference, but also develop new technologies by expanding Hilbert space in more DoFs.

quant-ph↗

arXiv2022

Experimental Demonstration of Quantum Pseudotelepathy

Quantum pseudotelepathy is a strong form of nonlocality. Different from the conventional non-local games where quantum strategies win statistically, e.g., the Clauser-Horne-Shimony-Holt game, quantum pseudotelepathy in principle allows quantum players to with probability 1. In this work, we report a faithful experimental demonstration of quantum pseudotelepathy via playing the non-local version of Mermin-Peres magic square game, where Alice and Bob cooperatively fill in a 3 by 3 magic square. We adopt the hyperentanglement scheme and prepare photon pairs entangled in both the polarization and the orbital angular momentum degrees of freedom, such that the experiment is carried out in a resource-efficient manner. Under the locality and fair-sampling assumption, our results show that quantum players can simultaneously win all the queries over any classical strategy.

quant-ph↗

arXiv2022

Nonlinear manipulation of orbital angular momentum spectra with second- and third- harmonic generation in a quasi-periodically poled crystal

Optical orbital angular momentum (OAM), as an important degree of freedom of light, has been attracted extensive attention, due to its intrinsic feature of natural discrete infinite dimension. Manipulation of OAM spectra is crucial for many impressive applications from classical to quantum realms, in particular, nonlinear manipulation of OAM spectra. Here we realized the nonlinear manipulation of OAM spectra by using the simultaneous second- and third-harmonic generation in a single nonlinear crystal of quasi-periodically poled potassium titanyl phosphate, for fundamental waves with a variety of OAM spectra, especially for customized OAM spectra of the second and third harmonics. The experimental results confirmed the theoretical predictions. Our approach not only provides a novel way to manipulate OAM spectra at new shorter wavelengths that are hard to be directly generated, but also may find new applications towards multiplexing in classical optics and high-dimensional information processing in quantum optics.

physics.optics↗

arXiv2022

Third-harmonic generation of spatially structured light in a quasi-periodically poled crystal

Nonlinear optical processes of spatially structured light, including optical vortex and vector optical fields, have stimulated a lot of interesting physical effects and found a variety of important applications ranging from optical imaging to quantum information processing. However, high harmonic generation of vector optical fields with space-varying polarization states is still a challenge. Here we demonstrate third harmonic generation of spatially structured light including vector optical fields, in a nonlinear Sagnac interferometer containing a carefully designed quasi-periodically poled potassium titanyl phosphate for the first time. The experimental results are in good agreement with the theoretical predictions. Our results will enable to manipulate spatially structured light or photons at new wavelengths and carrying higher orbital angular momentum. Our approach has the potential applications for the research of optical skyrmions and may open up new opportunities to produce spatially structured entangled photons for quantum communication and computation.

physics.optics↗

arXiv2021

Experimental self-testing for photonic graph states

Graph states -- one of the most representative families of multipartite entangled states, are important resources for multiparty quantum communication, quantum error correction, and quantum computation. Device-independent certification of highly entangled graph states plays a prominent role in the quantum information processing tasks. Here we have experimentally demonstrated device-independent certification for multipartite graph states, by adopting the robust self-testing scheme based on scalable Bell inequalities. Specifically, the prepared multi-qubit Greenberger-Horne-Zeilinger (GHZ) states and linear cluster states achieve a high degree of Bell violation, which are beyond the nontrivial bounds of the robust self-testing scheme. Furthermore, our work paves the way to the device-independent certification of complex multipartite quantum states.

quant-ph↗

arXiv2020

Polarization interferometric prism: a versatile tool for generation of vector fields, measurement of topological charges and implementation of a spin-orbit Controlled-Not gate

Optical vortex and vector field are two important types of structured optical fields. Due to their wide applications and unique features in many scientific realms, the generation, manipulation and measurement of such fields have attracted significant interest and become very important topics. However, most ways to generate vector fields have a trade-off among flexibility, efficiency, stability, and simplicity. Meanwhile, an easy and direct way to measure the topological charges, especially for high order optical vortex, is still a challenge. Here we design and manufacture a prism: polarization interferometric prism (PIP) as a single-element interferometer, which can conveniently convert an optical vortex to vector fields with high efficiency and be utilized to precisely measure the topological charge (both absolute value and sign) of an arbitrary optical vortex, even with a high order. Experimentally we generate a variety of vector fields with global fidelity ranging from 0.963 to 0.993 and measure the topological charge of an optical vortex by counting the number of petals uniformly distributed over a ring on the output intensity patterns. As a versatile tool to generate, manipulate and detect the spin-orbital state of single photons, PIP can also work in single-photon regime for quantum information processing. In experiment, the PIP is utilized as a spin-orbit Controlled-Not gate on the generated 28 two-qubit states, achieving the state fidelities ranging from 0.966 to 0.995 and demonstrating the feasibility of the PIP for single photons.

physics.optics↗