On-chip Path Research Articles

Integrated silicon photonics chip fabricated by CMOS compatible technology for low-bit-error-rate quantum key distribution

Quantum communication has extremely high security and is a development direction of future communication networks. In this paper, an on-chip path, off-chip polarization encoded quantum key distribution (QKD) chip is designed and fabricated using advanced silicon photonics fabrication technology. Using a special two-dimensional grating, we can convert light of different path states into corresponding polarization states and propagate in fiber. The performance of the basic optics, waveguides, gratings, and Mach–Zehnder interferometers on the chip is characterized. In the demonstrated QKD experiment, the quantum bit error rate is as low as 1.08%. It provides an important device for the future development of advanced integrated quantum information.

On-chip path encoded photonic quantum Toffoli gate

The quantum Toffoli gate is one of the most important three-qubit gates, but it is challenging to construct a chip according to the complicated traditional circuit. Using the optimized 3D configuration with an overpass waveguide to reduce the circuit complexity, we successfully fabricate an on-chip path encoded photonic quantum Toffoli gate enabled by the 3D capability of the femtosecond laser direct writing (FLDW) for the first time to our knowledge, whose truth-table fidelity is higher than 85.5%. Furthermore, a path encoded four-qubit controlled-controlled-controlled NOT gate is written to confirm the scalability of this resource-saving technique. This work paves the way for the FLDW of more complex and powerful photonic quantum computation chips.

On-Chip Integrated Single Photon Source-Optically Resonant Metastructure Based Scalable Quantum Optical Circuits

We present an approach to realizing on-chip optical quantum information processing (QIP) systems comprising (1) single photon source (SPS) arrays, here based on a new class of ordered single quantum dots of controlled size and shape named Mesa-top Single Quantum Dots (MTSQDs) that are naturally integrable in scalable architectures with (2) on-chip light manipulating units (LMUs) based upon either the conventional 2D photonic crystal platform or metastructures made of subwavelength size dielectric building blocks (DBBs) whose collective Mie-like optical resonances provide, simultaneously, all the needed light manipulating functions. The MTSQDs can provide high spectral uniformity with as-grown pairs emitting within $300\mu $ eV—thus calling for exploration of pathways for implementing on-chip SPS-SPS coupling for quantum entanglement. To this end, we present here simulation results for two different DBB-based implementations of scalable photon entanglement in MTSQD-DBB LMU coupled system.: (1) DBB array based nanoantenna-waveguide-beamsplitter-beamcombiner metastructures around the MTSQD SPSs that exploit primarily their collective magnetic dipole mode to simultaneously provide Purcell enhancement, enhanced emission directionality, waveguiding, beamspliting and beamcombining, thus enabling on-chip path entanglement via indirect coupling between the SPSs; (2) two MTSQDs coupled directly via the collective magnetic dipole mode of a back-to-back nanoantenna-waveguide structure. In either case, the long-distance coupled MTSQD-DBB structural units constitute the primitives for building complex quantum optical circuits.

A High-Precision Wide Range On-Chip Path Delay Measurement

On- chip delay measurement is one of the important procedures while the testing of the integrated circuits(IC) circuits is taken into consideration. Occurrence of the on chip delay is due to some defect in the IC at electrical level. Due to that defect there will be a delay in the movement of the signal to the destination. In order to improve the quality of shippable products, there is an urgent need to conduct effective delay testing for ascertaining the operation of chips at the rated frequency. In this paper, we present a on-chip path delay measurement architecture for efficiently detecting and debugging of delay faults in the fabricated integrated circuits. In the proposed on-chip path delay measurement(OCDM) circuit, several delay stages are employed, whose delay range is increased by a factor of two from the last to first delay stage. A calibration circuit is included to calibrate the delay range of the delay stage. Xilinx ISE based implementation was carried out. Simulation results shows precise measurement of path delays.

A High-Precision On-Chip Path Delay Measurement Architecture

In this paper, we present a novel on-chip path delay measurement architecture for efficiently detecting and debugging of delay faults in the fabricated integrated circuits. Several delay stages are employed in the proposed on-chip path delay measurement (OCDM) circuit, whose delay ranges are increased by a factor of two gradually from the last to the first delay stage. Thus, the proposed OCDM circuit can achieve a large delay measurement range with a small quantity of delay stages. A calibration circuit is incorporated into the proposed on-chip path delay measurement technique to calibrate the delay range of the delay stage under process variations. In addition, delay calibration for import lines is conducted to improve the precision of path delay measurement. Experimental results are presented to validate the proposed path delay measurement architecture.

Scalable fiber integrated source for higher-dimensional path-entangled photonic quNits

Integrated photonic circuits offer the possibility for complex quantum optical experiments in higher-dimensional photonic systems. However, the advantages of integration and scalability can only be fully utilized with the availability of a source for higher-dimensional entangled photons. Here, a novel fiber integrated source for path-entangled photons in the telecom band at 1.55\mum using only standard fiber technology is presented. Due to the special design the source shows good scalability towards higher-dimensional entangled photonic states (quNits), while path entanglement offers direct compatibility with on-chip path encoding. We present an experimental realization of a path-entangled two-qubit source. A very high quality of entanglement is verified by various measurements, i.a. a tomographic state reconstruction is performed leading to a background corrected fidelity of (99.45+-0.06)%. Moreover, we describe an easy method for extending our source to arbitrarily high dimensions.