More Like this

1. A scalable cavity-based spin–photon interface in a photonic integrated circuit

   https://doi.org/10.1364/OPTICAQ.509233  

   Chen, Kevin C. ; Christen, Ian ; Raniwala, Hamza ; Colangelo, Marco ; De Santis, Lorenzo ; Shtyrkova, Katia ; Starling, David ; Murphy, Ryan ; Li, Linsen ; Berggren, Karl ; et al ( April 2024 , Optica Quantum)

   A central challenge in quantum networking is transferring quantum states between different physical modalities, such as between flying photonic qubits and stationary quantum memories. One implementation entails using spin–photon interfaces that combine solid-state spin qubits, such as color centers in diamond, with photonic nanostructures. However, while high-fidelity spin–photon interactions have been demonstrated on isolated devices, building practical quantum repeaters requires scaling to large numbers of interfaces yet to be realized. Here, we demonstrate integration of nanophotonic cavities containing tin-vacancy (SnV) centers in a photonic integrated circuit (PIC). Out of a six-channel quantum microchiplet (QMC), we find four coupled SnV-cavity devices with an average Purcell factor of ∼7. Based on system analyses and numerical simulations, we find with near-term improvements this multiplexed architecture can enable high-fidelity quantum state transfer, paving the way toward building large-scale quantum repeaters.

    

   more » « less
2. Graph states of atomic ensembles engineered by photon-mediated entanglement

   https://doi.org/10.1038/s41567-024-02407-1  

   Cooper, Eric S. ; Kunkel, Philipp ; Periwal, Avikar ; Schleier-Smith, Monika ( March 2024 , Nature Physics)

   Graph states are a broad family of entangled quantum states, each defined by a graph composed of edges representing the correlations between subsystems. Such states constitute versatile resources for quantum computation and quantum-enhanced measurement. Their generation and engineering require a high level of control over entanglement. Here we report on the generation of continuous-variable graph states of atomic spin ensembles, which form the nodes of the graph. We program the entanglement structure encoded in the graph edges by combining global photon-mediated interactions in an optical cavity with local spin rotations. By tuning the entanglement between two subsystems, we either localize correlations within each subsystem or enable Einstein–Podolsky–Rosen steering—a strong form of entanglement that enables the extraction of precise information from one subsystem through measurements on the other. We further engineer a four-mode square graph state, highlighting the flexibility of our approach. Our method is scalable to larger and more complex graphs, laying groundwork for measurement-based quantum computation and advanced protocols in quantum metrology.

    

   more » « less
3. Microwave-Based Quantum Control and Coherence Protection of Tin-Vacancy Spin Qubits in a Strain-Tuned Diamond-Membrane Heterostructure

   https://doi.org/10.1103/PhysRevX.13.041037  

   Guo, Xinghan ; Stramma, Alexander M. ; Li, Zixi ; Roth, William G. ; Huang, Benchen ; Jin, Yu ; Parker, Ryan A. ; Arjona Martínez, Jesús ; Shofer, Noah ; Michaels, Cathryn P. ; et al ( November 2023 , Physical Review X)

   Robust spin-photon interfaces in solids are essential components in quantum networking and sensing technologies. Ideally, these interfaces combine a long-lived spin memory, coherent optical transitions, fast and high-fidelity spin manipulation, and straightforward device integration and scaling. The tin-vacancy center (SnV) in diamond is a promising spin-photon interface with desirable optical and spin properties at 1.7 K. However, the SnV spin lacks efficient microwave control, and its spin coherence degrades with higher temperature. In this work, we introduce a new platform that overcomes these challenges—SnV centers in uniformly strained thin diamond membranes. The controlled generation of crystal strain introduces orbital mixing that allows microwave control of the spin state with 99.36(9)% gate fidelity and spin coherence protection beyond a millisecond. Moreover, the presence of crystal strain suppresses temperature-dependent dephasing processes, leading to a considerable improvement of the coherence time up to 223(10) μs at 4 K, a widely accessible temperature in common cryogenic systems. Critically, the coherence of optical transitions is unaffected by the elevated temperature, exhibiting nearly lifetime-limited optical linewidths. Combined with the compatibility of diamond membranes with device integration, the demonstrated platform is an ideal spin-photon interface for future quantum technologies. 

   more » « less
4. On-chip spin-orbit locking of quantum emitters in 2D materials for chiral emission

   https://doi.org/10.1364/OPTICA.463481  

   Ma, Yichen ; Zhao, Haoqi ; Liu, Na ; Gao, Zihe ; Mohajerani, Seyed Sepehr ; Xiao, Licheng ; Hone, James ; Feng, Liang ; Strauf, Stefan ( August 2022 , Optica)

   Light carries both spin angular momentum (SAM) and orbital angular momentum (OAM), which can be used as potential degrees of freedom for quantum information processing. Quantum emitters are ideal candidates towards on-chip control and manipulation of the full SAM–OAM state space. Here, we show coupling of a spin-polarized quantum emitter in a monolayer${\mathrm{W}\mathrm{S}\mathrm{e}}_2$with the whispering gallery mode of a${\mathrm{S}\mathrm{i}}_3{\mathrm{N}}_4$ring resonator. The cavity mode carries a transverse SAM of$\mathrm{\sigma <\#comment/>}=\pm <\#comment/>1$in the evanescent regions, with the sign depending on the orbital power flow direction of the light. By tailoring the cavity–emitter interaction, we couple the intrinsic spin state of the quantum emitter to the SAM and propagation direction of the cavity mode, which leads to spin–orbit locking and subsequent chiral single-photon emission. Furthermore, by engineering how light is scattered from the WGM, we create a high-order Bessel beam which opens up the possibility to generate optical vortex carrying OAM states.

    

   more » « less
5. On the dissipative dynamics of entangled states in coupled-cavity quantum electrodynamics arrays

   https://doi.org/10.1364/JOSAB.441224  

   Mirza, Imran M. ; Cruz, Adriana S. ( December 2021 , Journal of the Optical Society of America B)

   We examine the dissipative dynamics of N00N states with an arbitrary photon number$\mathcal{N}$in two architectures of fiber-coupled optical ring resonators (RRs) interacting with two-level quantum emitters (QEs). One architecture consists of a two-way cascaded array of emitter–cavity systems, while in the other architecture, we consider two fiber-coupled RRs, each coupled to multiple dipole–dipole interacting (DDI) QEs. Our focus in this paper is to study how an initially prepared multiple excitation atomic N00N state transfers to the RRs and then how rapidly it decays in these open cavity quantum electrodynamics setups while varying the emitter–cavity coupling strengths, emitter–cavity detuning, and backscattering from cavity modes. We present a general theoretical formalism valid for any arbitrary numbers of QEs, RRs, and$\mathcal{N}$numbers in the N00N state for both schemes. As examples, we discuss the cases of single- and two-excitation N00N states and report the comparison of our findings in both schemes. As one of the main results, we conclude that the array scheme tends to store N00N for longer times, while the DDI scheme supports higher fidelity values. The results of this study may find applications in designing new multiparty entanglement-based protocols in quantum metrology and quantum lithography.

    

   more » « less