Electro-mechanical control of an on-chip optical beam splitter containing an embedded quantum emitter

Two-axis MEMS positioner for waveguide alignment in silicon nitride photonic integrated circuits

Alignment is critical for efficient integration of photonic integrated circuits (PICs), and microelectromechanical systems (MEMS) actuators have shown potential to tackle this issue. In this work, we report MEMS positioning actuators designed with the ultimate goal of aligning silicon nitride (SiN) waveguides either to different outputs within a SiN chip or to active chips, such as lasers and semiconductor optical amplifiers. For the proof-of-concept, suspended SiN waveguides implemented on a silicon-on-insulator wafer were displaced horizontally in the direction of light propagation to close an initial gap of 6.92 µm and couple the light to fixed output waveguides located on a static section of the chip. With the gap closed, the suspended waveguides showed ∼ 345 nm out-of-plane misalignment with respect to the fixed waveguides. The suspended waveguides can be displaced laterally by more than ±2 µm. When the waveguides are aligned and the gap closed, an average loss of -1.6 ± 0.06 dB was achieved, whereas when the gap is closed with a ± 2 µm lateral displacement, a maximum average loss of ∼ -19.00 ± 0.62 dB was obtained. The performance of this positioner does not only pave the way for active chip alignment, but it could also be considered for optical switching applications.

Creating and concentrating quantum resource states in noisy environments using a quantum neural network

Quantum information processing tasks require exotic quantum states as a prerequisite. They are usually prepared with many different methods tailored to the specific resource state. Here we provide a versatile unified state preparation scheme based on a driven quantum network composed of randomly-coupled fermionic nodes. The output of such a system is then superposed with the help of linear mixing where weights and phases are trained in order to obtain desired output quantum states. We explicitly show that our method is robust and can be utilized to create almost perfect maximally entangled, NOON, W, cluster, and discorded states. Furthermore, the treatment includes energy decay in the system as well as dephasing and depolarization. Under these noisy conditions we show that the target states are achieved with high fidelity by tuning controllable parameters and providing sufficient strength to the driving of the quantum network. Finally, in very noisy systems, where noise is comparable to the driving strength, we show how to concentrate entanglement by mixing more states in a larger network.

Strain-Tunable Quantum Integrated Photonics

Semiconductor quantum dots are crucial parts of the photonic quantum technology toolbox because they show excellent single-photon emission properties in addition to their potential as solid-state qubits. Recently, there has been an increasing effort to deterministically integrate single semiconductor quantum dots into complex photonic circuits. Despite rapid progress in the field, it remains challenging to manipulate the optical properties of waveguide-integrated quantum emitters in a deterministic, reversible, and nonintrusive manner. Here we demonstrate a new class of hybrid quantum photonic circuits combining III-V semiconductors, silicon nitride, and piezoelectric crystals. Using a combination of bottom-up, top-down, and nanomanipulation techniques, we realize strain tuning of a selected, waveguide-integrated, quantum emitter and a planar integrated optical resonator. Our findings are an important step toward realizing reconfigurable quantum-integrated photonics, with full control over the quantum sources and the photonic circuit.