Daryl Achilles

Fiber-assisted detection with photon number resolution

We report the development of a photon-number-resolving detector based on a fiber-optical setup and a pair of standard avalanche photodiodes. The detector is capable of resolving individual photon numbers and operates on the well-known principle by which a single-mode input state is split into a large number (eight) of output modes. We reconstruct the photon statistics of weak coherent input light from experimental data and show that there is a high probability of inferring the input photon number from a measurement of the number of detection events on a single run.

Photon-number-resolving detection using time-multiplexing

A time-multiplexed detector capable of photon number resolution was constructed. The detector is analyzed theoretically and used to verify the photon statistics of weak coherent light. Conditional state preparation using the detector is explored

Characterization and Preparation of Higher Photon Number States

The ability to create and characterize photon number states is of utmost importance in most optically‐implemented quantum information schemes. In the past, progress in this area has been hindered by a lack of photodetectors that are both highly efficient and can discriminate different photon number states. We have utilized a time‐multiplexed detector to characterize the properties of a heralded photon source based on parametric downconversion. We also show that the different losses in our detector can be described by a single loss parameter, greatly simplifying the data analysis.

Fast quantum key distribution with decoy number states

We investigate the use of photon number states to identify eavesdropping attacks on quantum key distribution (QKD) schemes. The technique is based on the fact that different photon numbers traverse a channel with different transmittivity. We then describe two QKD schemes that utilize this method, one of which overcomes the upper limit on the key generation rate imposed by the dead time of detectors when using a heralded source of photons.

Loss-tolerant characterization of nonclassical photonic states

We experimentally investigate a method of directly characterizing the photon number distribution of nonclassical light that is tolerant to losses; makes use of standard binary detectors; and only requires a single set of measurements.

Experimental multiphoton conditional state preparation and analysis

A time-multiplexed detector capable of photon number resolution was used to investigate the photon statistics of a heralded photon source based on parametric downconversion in a quasi-phasematched KTP waveguide.

Characterization of parametric downconversion in the photon number basis

Parametric downconversion in a quasi-phase matched KTP waveguide offers the possibility to implement a highly efficient source of photonic states. We investigate the photon statistics of such a source with a time-multiplexed detector, which is capable of photon number resolution.

Conditional Preparation of High‐Fidelity Single‐Photon Wavepackets

The reliable generation of true single‐photon wavepackets with well‐defined modal structure is a crucial ingredient for the realization of linear optical quantum computing. We have implemented a highly efficient waveguided parametric downconversion source pumped by ultrashort pulses, which is characterized by the spatial decoupling of the signal and idler photon while exhibiting a conditional detection efficiency of 51%, corresponding to a preparation efficiency of 85%. We have performed various tests to confirm the single‐photon character of the conditionally prepared state.