RAISE: TAQS: Two-Photon Quantum Photonic Logic Gates Enabled by Photonic Bound States

量子信息科学利用叠加和纠缠等量子力学现象来改进经典的通信、计算、信息处理和精确测量。量子技术有望在加强国家安全和支持进一步的科学发现方面发挥决定性作用。在量子信息处理中，单量子比特（qubit）操作不足以释放量子比特集合所赋予的所有计算能力。因此，在有限的单量子位门上添加一个双量子位门（如控制相位门）是必要的，实际上也是足够的，以实现在经典计算机上不再能够有效模拟的目标。在光量子计算中，光子量子比特由于其低噪声、长相干时间、光速传输和易于使用标准光学元件在单量子比特级别操作而被用作信息载体。迄今为止，只有基于线性光学和光子探测器的概率双量子位光子逻辑门被证明。然而，实施过程涉及大量的资源开销，并要求严格的技术要求，这在今天仍然具有挑战性。该项目通过开发确定性控制相门来解决基本挑战，以实现量子计算的全部潜力。教育和推广活动将培养下一代量子科学家和工程师，以加快量子信息科学和应用的步伐。技术摘要：本研究的目标是利用一种全新的方法，基于光子二聚体态、手性纳米光子波导和单偶极子发射器的产生，开发一种新的技术方法来实现两个光子量子比特的控制相位门。在纳米光子波导中，横向上的严格光约束使得人们可以将偶极子发射器放置在手性点上，并实现光子与发射器之间的强耦合，从而使散射光子有效地耦合到正向传播模式而不是反向传播模式。相关光子形成光子二聚体，这是光子的束缚态，并产生非平凡的传输pi相移。控制相位门的验证将通过一种基于集成波导方法和数字分辨光子探测器的新型实验设计来实现。光子二聚体状态的演示以及与双光子与偶极子发射器相互作用的状态相关的相应180度相移将是展示光子量子计算潜力的重要一步。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Quantum information science exploits quantum mechanical phenomena such as superposition and entanglement to improve classical communication, computation, information processing, and precision measurement. Quantum technology is expected to play a decisive role in enhancing national security and bolstering further scientific discovery. In quantum information processing, single-quantum bit (qubit) operations are not sufficient to unlock all the computational power that is endowed by a collection of qubits. Hence it is necessary and in fact sufficient to add a two-qubit gate such as a controlled-phase gate to a finite set of single-qubit gates to achieve what no longer can be efficiently simulated on a classical computer. In optical quantum computation, photonic qubits are used as information carriers due to their low-noise, long coherence times, light-speed transmission and ease of manipulation at the single-qubit level using standard optical components. To date, only probabilistic two-qubit photonic logic gates based on linear optics and photon detectors have been demonstrated. The implementation, however, is associated with substantial resource overhead and demands stringent technological requirements which are still challenging today. This project addresses the fundamental challenges by developing a deterministic controlled-phase gate to realize the full potential of quantum computation. The educational and outreach activities will train the next-generation quantum scientists and engineers to accelerate the pace of quantum information science and applications. Technical Abstract:The goal of this work is to develop a new technological approach to a controlled-phase gate for two photonic qubits using an entirely novel approach based on the generation of photonic dimer states, a chiral nano-photonic waveguide, and a single dipole emitter. The tight optical confinement in the transverse direction in the nanophotonic waveguide allows one to place the dipole emitter at the chiral point and achieve strong coupling between the photon and the emitter such that the scattered photons couple efficiently to the forward but not the backward-propagating mode. The correlated photons form the photonic dimers, which are the bound states of photons and give rise to a non-trivial transmission pi phase shift. The validation of the controlled-phase gate will be achieved using a novel experimental design based on an integrated waveguide approach coupled with number-resolved photon detectors. The demonstration of the photonic dimer state and the corresponding 180-degree phase shift associated with the state with both photons interacting with the dipole emitter will be a major step forward in demonstrating the potential of photonic quantum computing.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.