scholarly journals Quantum interference enables constant-time quantum information processing

2019 ◽  
Vol 5 (7) ◽  
pp. eaau9674 ◽  
Author(s):  
M. Stobińska ◽  
A. Buraczewski ◽  
M. Moore ◽  
W. R. Clements ◽  
J. J. Renema ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Information Processing ◽  
Quantum Interference ◽  
Quantum Information Processing ◽  
Arbitrary Length ◽  
Input Size ◽  
Time Quantum ◽  
Speed Up ◽  
One Step ◽  
Open Question

It is an open question how fast information processing can be performed and whether quantum effects can speed up the best existing solutions. Signal extraction, analysis, and compression in diagnostics, astronomy, chemistry, and broadcasting build on the discrete Fourier transform. It is implemented with the fast Fourier transform (FFT) algorithm that assumes a periodic input of specific lengths, which rarely holds true. A lesser-known transform, the Kravchuk-Fourier (KT), allows one to operate on finite strings of arbitrary length. It is of high demand in digital image processing and computer vision but features a prohibitive runtime. Here, we report a one-step computation of a fractional quantum KT. The quantum d-nary (qudit) architecture we use comprises only one gate and offers processing time independent of the input size. The gate may use a multiphoton Hong-Ou-Mandel effect. Existing quantum technologies may scale it up toward diverse applications.

scholarly journals Synchronization of optical photons for quantum information processing

2016 ◽  
Vol 2 (5) ◽  
pp. e1501772 ◽  
Author(s):  
Kenzo Makino ◽  
Yosuke Hashimoto ◽  
Jun-ichi Yoshikawa ◽  
Hideaki Ohdan ◽  
Takeshi Toyama ◽  
...  
Keyword(s):  
Information Processing ◽  
Quantum Information ◽  
High Purity ◽  
Quantum Interference ◽  
Quantum Information Processing ◽  
Single Photon ◽  
Arrival Times ◽  
Optical Photons ◽  
Storage Times ◽  
First Time

A fundamental element of quantum information processing with photonic qubits is the nonclassical quantum interference between two photons when they bunch together via the Hong-Ou-Mandel (HOM) effect. Ultimately, many such photons must be processed in complex interferometric networks. For this purpose, it is essential to synchronize the arrival times of the flying photons and to keep their purities high. On the basis of the recent experimental success of single-photon storage with high purity, we demonstrate for the first time the HOM interference of two heralded, nearly pure optical photons synchronized through two independent quantum memories. Controlled storage times of up to 1.8 μs for about 90 events per second were achieved with purities that were sufficiently high for a negative Wigner function confirmed with homodyne measurements.

scholarly journals Photon engineering for quantum information processing

2003 ◽  
Vol 3 (special) ◽  
pp. 480-502
Author(s):  
A.B. U'Ren ◽  
K. Banaszek ◽  
I.A. Walmsley
Keyword(s):  
Information Processing ◽  
Quantum Information ◽  
Quantum Interference ◽  
Quantum Information Processing ◽  
Logic Gate ◽  
Optical Systems ◽  
Two Photon ◽  
Entangled Photon Pairs ◽  
Available Technology ◽  
Photon States

We study distinguishing information in the context of quantum interference involving more than one parametric downconversion (PDC) source and in the context of generating polarization-entangled photon pairs based on PDC. We arrive at specific design criteria for two-photon sources so that when used as part of complex optical systems, such as photon-based quantum information processing schemes, distinguishing information between the photons is eliminated guaranteeing high visibility interference. We propose practical techniques which lead to suitably engineered two-photon states that can be realistically implemented with available technology. Finally, we study an implementation of the nonlinear-sign shift (NS) logic gate with PDC sources and show the effect of distinguishing information on the performance of the gate.

PREPARATION AND MANIPULATION OF W-CLASS ENTANGLED STATES: APPLICATIONS TO QUANTUM-INFORMATION PROCESSING

2009 ◽  
Vol 07 (02) ◽  
pp. 493-504 ◽  
Author(s):  
XIN-WEN WANG
Keyword(s):  
Information Processing ◽  
Quantum Information ◽  
Quantum Electrodynamics ◽  
Quantum Information Processing ◽  
Cavity Quantum Electrodynamics ◽  
Separable State ◽  
Special Configuration ◽  
State Formula ◽  
One Step ◽  
Step Generation

We propose a cavity-quantum-electrodynamics scheme for one-step generation of the special configuration of W-class state [Formula: see text] which can implement deterministic teleportation, superdense coding, quantum-information splitting, and phase-covariant telecloning. We also present a method for one-step realization of a nontrivial unitary transformation [Formula: see text] which can transform a standard W state into a fully separable state. The [Formula: see text] operation plays a key role in recently proposed quantum-information processing tasks. Both the schemes are robust against decoherence. In addition, they can endure the error of controlling the interaction time between atoms and cavity. Our ideas can also be generalized to other systems.

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