Overview of this Project
Quantum Superposition and Quantum Entanglement (Greenberger, Horne, & Zeilinger, Phys. Today 46 (8), 22 (Aug. 1993); R. Horodecki et al., Rev. Mod. Phys. 81, 865 (2009)) are bed rocks on which current paradigm of quantum information is resting. Superposition and entanglement are playing pivotal role for building next generation of quantum information technology (QIT) such as quantum computer and quantum internet. Quantum computer is a next generation of computing machine, which is exponentially faster than present-day classical digital computers. Quantum internet is a next generation of computer internet, which has exponentially larger state-space that allow much more efficient & secure information transfer then present-day classical computer internet.
This research project is based on quantum entanglement (Click For: Quantum Entanglement ) and its applications to development of next generation of atom-photon quantum network . Entanglement is at the heart of quantum mechanics and is central to the entire paradigm of quantum information science (QIS). Entanglement was the subject of recent Physics Nobel Prize (Click: Nobel-Prize-2022/). This Physics Nobel Prize was awarded for pioneering quantum information science experiments using entangled photons. Therefore, entanglement is currently a very hot topic of research. Development of artificial intelligence (AI) systems such as neural network, using principles of physics, was the subject of recent Physics Nobel Prize (Click: Physics-Nobel-Prize-2024). Atom-photon quantum network, like neural network, is also an artificial intelligence (AI) system. Therefore, development of atom-photon quantum network using techniques of atomic physics, entanglement, and photons is a subject of very intense research in quantum physics, quantum optics, quantum information science (QIS), and artificial intelligence (AI).
My current research work is on multi-qubit entanglement in Graph States ((M. Hein, J. Eisert, & H. J. Briegel, Phys. Rev. A 69, 062311 (2004)) (Click For: Multipartite Entanglement) and its applications to multi-qubit quantum teleportation/ multi-qubit entanglement swapping/ multi-party quantum communication experiments, which leads to development of Quantum network (Click For: Quantum Network). Entanglement in multi-qubit states is more complicated than in two-qubit entanglement. Multi-qubit quantum entangled states used in this project are Greenberger-Horne-Zeilinger (GHZ) State (Click: GHZ), Cluster State (Click: CLUSTER), Brown State ( I. D. K. Brown et al., J. Phys. A 38 (5), 1119-1131 (2005))(Click: BROWN), and Borras State (A. Borras et al., J. Phys. A 40 (44), 13407-13421 (2007)) (Click: BORRAS). Such multi-qubit entangled states have bizarre quantum properties, which are not observed in two-qubit entanglement. Theoretically, the subject of multi-qubit entanglement is very poorly understood, and experimentally very little work has been done on multi-qubit entanglement. Further, multi-qubit entanglement give rise to striking contradiction with local realism for non statistical prediction of quantum mechanics. Multi-qubit entangled states can be synthesized in single cold atoms in high-finesse Fabry-Perot cavities, in cold atoms in the optical lattice, in atomic ions in the ion trap, and in entangled photons generated by spontaneous parametric down conversion (SPDC) in nonlinear solid-state crystals. Multi-qubit entangled states are used to test foundation of quantum mechanics and to improve detection sensitivity and precision of measurement in atomic and molecular spectroscopy (D. J. Wineland et al., Science 304, 1476 (2004)). Such multi-qubit states are also used to establish quantum interconnections (QuICs) (D. Awschalom et al., PRX Quantum 2, 017002 (2021); J. Wang et al., Optica 3 (4), 407 (2016)) amomg nodes of a quantum network and among different units of a quantum computer. Therefore, multi-qubit entangled states are essential for building the next generation of quantum information technology (QIT), such as modular quantum computers & Global scale quantum internet.
In this atom-photon quantum network project, nodes of the network are represented by quantum memories, which are designed using hyperfine levels in the neutral Cesium (Cs) atoms and multi-photon quantum entangled states are generated by nonlinear optical technique of chirped-pulse (Physics Nobel Prize Click: (Nobel-Prize-2018)) spontaneous parametric down-conversion (SPDC) of ultrafast (/femtosecond) optical pulses in solid-state nonlinear optical crystals. These laboratories generated multi-photon entangled states are distributed to remotely located nodes of a quantum network. Due to entanglement among the distributed photons, nodes get quantum mechanically interconnected. We then conduct multi-party quantum teleportation experiments, which are useful for understanding communication of quantum information both within quantum computers & among nodes of a quantum networks. My recent published research (Elementary Tripartite Quantum Communication Photonic Network at the Telecom Wavelength, P. S. Bhatia, Laser Physics 31 (9), 095203 (2021)) shows that in multi-party teleportation, unlike in two-party (Alice and Bob) teleportation (C. H. Bennett et al., Phys. Rev. Lett. 70, 1895 (1993)), qubit to be teleported is first split into fragments and then at the destination station original qubit is reconstructed from the fragments. This published research also shows that for development of quantum network, teleportation alone is not sufficient, but development of quantum network imposes additional requirements. One such requirement is the separability property of quantum channel, which is used to interconnect different nodes of the network. Another such requirement is the quantum error correction (QEC) within the network. My recent published research ((Long-Distance Multi-Party Quantum Teleportation for Quantum Networking Using Multi-Qubit Entanglement Swapping, P. S. Bhatia, Phys. Rev. X Quantum)) also shows that with technique of multi-qubit entanglement swapping, two (or more) fully separated quantum networks with smaller number of nodes can be merged to design a quantum network with larger number of nodes.
This is a large-scale and very sophisticated atom-photon experiment, which uses special purpose high repetition rate ultrafast (femtosecond) lasers & the latest and the most advanced quantum information technology such as superconducting nanowire photon number resolving (PNR) single photon detectors (SNSPD) in the laboratory.
The ultimate goal of this project is to experimentally demonstrate a multi-node Atom-Photon Quantum Network, which is a very tough & hard experimental goal to achieve.
Research presented in this project is original and is significant contribution, with high potential impact, to very rapidly advancing field of quantum science and technology.
This research is important for the development of the next generation of quantum internet. Majority of other researchers, at different universities, are using two-qubit EPR Bell-states, which can lead to communication only between two nodes of a quantum network. This is the only major project in the whole United State, which employs multi-qubit entangled states that leads to communication among nodes of a multi-node quantum network. Therefore, this project represents US leadership in the field of quantum communication. Within the broad field of quantum information science (QIS) and artificial intelligence (AI), development of quantum internet has been declared as a high priority research area by National Science Foundation (NSF) and US Department of Energy (DOE). This research work is also very important for National Security and Military Intelligence.
