Suman Karan

Indian Institute of Technology Kanpur | IIT Kanpur · Department of Physics

A K-mirror is a device that rotates the wavefront of an incident optical field. It has recently gained prominence over the Dove prism, another commonly used wavefront rotator, due to the fact that while a K-mirror has several controls for adjusting the internal reflections, a Dove prism is made of a single glass element with no additional control....

A K-mirror is a device that rotates the wavefront of an incident optical field. It has recently gained prominence over Dove prism, another commonly used wavefront rotator, due to the fact that while a K-mirror has several controls for adjusting the internal reflections, a Dove prism is made of a single glass element with no additional control. Thus...

High-dimensional entangled states in an orbital-angular-momentum (OAM) basis offer several unique advantages for quantum information applications. However, for the optimal performance of a given application, one requires a generation technique for OAM entangled states that is completely postselection-free and fully controllable. Nonetheless, despit...

Structured correlations are important for quantum imaging. We propose and experimentally demonstrate a method to structure spatial two-photon correlations in the near-field by controlling phase-matching. Entanglement witnessed in the near-field enables these structured two-photon correlations to be useful for entanglement-based applications.

We propose an OAM measurement technique with uniform efficiency for any general wideband state. We demonstrate our technique for up to 100-dimensional state with 99.85% accuracy at high light and single photon levels.

Structured correlations are important for quantum imaging. We propose and experimentally demonstrate a method to structure spatial two-photon correlations in the near-field by controlling phase-matching. Entanglement witnessed in the near-field enables these structured two-photon correlations to be useful for entanglement-based applications.

Dove prisms and K-mirrors are devices extensively used for rotating the wavefront of an optical field. These devices have several applications, including the measurement of orbital angular momentum, microscopy, beam steering, and pattern recognition. However, the wavefront rotation achieved through these devices is always accompanied by polarizatio...

Although the continuous-variable position-momentum entanglement of photon pairs produced by parametric down-conversion has applicability in several quantum information applications, it is not suitable for applications involving long-distance propagation. This is because entanglement in the position-momentum bases, as seen through Einstein-Podolsky-...

Dove prisms and K-mirrors are devices extensively used for rotating the wavefront of an optical field. These devices have several applications, including measurement of orbital angular momentum, microscopy, beam steering and pattern recognition. However, the wavefront rotation achieved through these devices is always accompanied by polarization cha...

High-dimensional entangled states in orbital angular momentum (OAM) basis offer unique advantages for several quantum information applications. However, a given quantum information application for its optimal performance requires generation of a specific OAM entangled state with full control over the shape of the OAM Schmidt spectrum. Spontaneous p...

The practical implementation of free-space quantum information tasks requires entanglement to be sustained over long distances and in the presence of turbulent and noisy environments. The transverse position-momentum entanglement of photon pairs produced by parametric down-conversion has found several uses in quantum information science, however, i...

We report the revival of angle-OAM entanglement through propagation. We find that the entanglement decays within a short distance. However, a further propagation induces revival in entanglement, and this feature remains intact in turbulence.

The existing techniques for measuring high-dimensional pure states of light in the orbital angular momentum (OAM) basis either involve a large number of single-pixel data acquisitions and substantial postselection errors that increase with dimensionality, involve substantial loss, or require interference with a reference beam of known phase. Here,...

The existing techniques for measuring high-dimensional pure states of light in the orbital angular momentum (OAM) basis either involve a large number of single-pixel data acquisitions and substantial postselection errors that increase with dimensionality, or involve substantial loss, or require interference with a reference beam of known phase. Her...

We propose a novel technique for measuring high-dimensional pure states of light in the orbital-angular-momentum (OAM) basis using only nine multipixel image acquisitions. We experimentally demonstrate the technique for laboratory-generated states up to 25 dimensions, reporting a mean fidelity greater than 90 % up to 11 dimensions.

Spontaneous parametric down-conversion (SPDC) is the most widely used process for generating photon pairs entangled in various degrees of freedom such as polarization, time-energy, position-transverse momentum, and angle-orbital angular momentum (OAM). In SPDC, a pump photon interacts with a nonlinear optical crystal and splits into two entangled p...