We investigate aspects, in various contexts, of entanglement and the wave particle duality. We show that the dynamics of tripartite systems which interact via one excitation exchange leads to a direct connection between entanglement sudden death and the appearance of genuine entanglement. We also show that this is valid (not with the same generality) also for a four partite system in the context of the double JaynesCummings model. Moreover we show that the entanglement dynamics in this case can be completely expressed in geometrical terms. Using the same system we show that by performing adequate Zeno like measurements it is possible to freeze, increase, or even revive the initial entanglement. This intriguing result is also associated to entanglement sudden death. As far as wave particle duality and entanglement are concerned we studied a particle going through an interferometer equipped with a whichway device. We quantified the quality of the probe and exhibit its connection with the availability of the whichway information provided by the probe system. When the probe system information is unaccessible only the particle character will be observed. We obtain limits for a good (quantum regime) and for a bad (classical regime) whichway detector (probe system). We used our results to interpret a recent experiment set up to test the quantumclassical border where the probe covers from the quantum to the classical limit. We showed that the experimental errors influenced the conclusion inferred form the data about having achieved the classical limit. Finally we analyze the Ramsey zones from the point of view of our findings and provide for a transparent physical interpretation. In this case the classical limit of the probe system is reached due to a source plus strong dissipation dynamics, which swaps whichway information to a system containing an infinite number of degrees of freedom, making thus sure that any whichway information becomes unavailable.We investigate aspects, in various contexts, of entanglement and the wave particle duality. We show that the dynamics of tripartite systems which interact via one excitation exchange leads to a direct connection between entanglement sudden death and the appearance of genuine entanglement. We also show that this is valid (not with the same generality) also for a four partite system in the context of the double JaynesCummings model. Moreover we show that the entanglement dynamics in this case can be completely expressed in geometrical terms. Using the same system we show that by performing adequate Zeno like measurements it is possible to freeze, increase, or even revive the initial entanglement. This intriguing result is also associated to entanglement sudden death. As far as wave particle duality and entanglement are concerned we studied a particle going through an interferometer equipped with a whichway device. We quantified the quality of the probe and exhibit its connection with the availability of the whichway information provided by the probe system. When the probe system information is unaccessible only the particle character will be observed. We obtain limits for a good (quantum regime) and for a bad (classical regime) whichway detector (probe system). We used our results to interpret a recent experiment set up to test the quantumclassical border where the probe covers from the quantum to the classical limit. We showed that the experimental errors influenced the conclusion inferred form the data about having achieved the classical limit. Finally we analyze the Ramsey zones from the point of view of our findings and provide for a transparent physical interpretation. In this case the classical limit of the probe system is reached due to a source plus strong dissipation dynamics, which swaps whichway information to a system containing an infinite number of degrees of freedom, making thus sure that any whichway information becomes unavailable.

Nov 18, 20110 citations

An Open Question

David Pogue

Scientific AmericanJan 18, 20111 citation

SELECTIVE POPULATION OF MOLECULAR CORE NONPENETRATING RYDBERG STATES

David Grimes, Robert W. Field, Ethan Klein +2 more

"Core nonpenetrating Rydberg states of molecules are a neglected state of matter. They could have a variety of uses, notably state-selective production of molecular ions. Due to the \textit{l}(\textit{l}+1)/r $^{2}$ centrifugal barrier that prevents the Rydberg electron in high-\textit{l} states from penetrating inside of the ion core, the electron is essentially uncoupled from the ion core, and the system becomes atom-like with long lifetimes, an ""almost good"" \textit{l} quantum number, and electronic transitions that follow $\Delta$ J $^{+}$ =0 and $\Delta$ v $^{+}$ =0 propensity rules. However, in most molecules access to these states, via a sequence of $\Delta$ \textit{l}=+1 transitions from low-n*, low-\textit{l} states, is blocked by the necessity to traverse the ""zone of death,"" in which nonradiative decay mechanisms are prohibitively fast. We exploit Chirped Pulse millimeter-Wave (CPmmW) spectroscopy to efficiently excite Ca atoms and BaF molecules to core nonpenetrating states in the absence of nonradiative decay mechanisms. A universal method for preparing core nonpenetrating Rydberg states of molecules, which combines CPmmW spectroscopy with STImulated Raman Adiabatic Passage (STIRAP), will be discussed.""Core nonpenetrating Rydberg states of molecules are a neglected state of matter. They could have a variety of uses, notably state-selective production of molecular ions. Due to the \textit{l}(\textit{l}+1)/r$^{2}$ centrifugal barrier that prevents the Rydberg electron in high-\textit{l} states from penetrating inside of the ion core, the electron is essentially uncoupled from the ion core, and the system becomes atom-like with long lifetimes, an ""almost good"" \textit{l} quantum number, and electronic transitions that follow $\Delta$J$^{+}$=0 and $\Delta$v$^{+}$=0 propensity rules. However, in most molecules access to these states, via a sequence of $\Delta$\textit{l}=+1 transitions from low-n*, low-\textit{l} states, is blocked by the necessity to traverse the ""zone of death,"" in which nonradiative decay mechanisms are prohibitively fast. We exploit Chirped Pulse millimeter-Wave (CPmmW) spectroscopy to efficiently excite Ca atoms and BaF molecules to core nonpenetrating states in the absence of nonradiative decay mechanisms. A universal method for preparing core nonpenetrating Rydberg states of molecules, which combines CPmmW spectroscopy with STImulated Raman Adiabatic Passage (STIRAP), will be discussed."

International Symposium on Molecular Spectroscopy (ISMS)Jun 19, 20140 citations

A Universe of Questions.

Yakov Borisovich Zeldovich

QuantumJan 1, 19921 citation

Quantum Control of Finite-time Disentanglement in Qubit-Qubit and Qubit-Qutrit Systems

Mazhar Ali

This thesis is a theoretical study of entanglement dynamics and its control of qubit-qubit and qubit-qutrit systems. In particular, we focus on the decay of entanglement of quantum states interacting with dissipative environments. Qubit-qubit entanglement may vanish suddenly while interacting with statistically independent vacuum reservoirs. Such finite-time disentanglement is called sudden death of entanglement(ESD). We investigate entanglement sudden death of qubit-qubit and qubit-qutrit systems interacting with statistically independent reservoirs at zero- and finite-temperature. It is shown that for zero-temperature reservoirs, some entangled states exhibit sudden death while others lose their entanglement only after infinite time. Thus, there are two possible routes of entanglement decay, namely sudden death and asymptotic decay. We demonstrate that starting with an initial condition which leads to finite-time disentanglement, we can alter the future course of entanglement by local unitary actions. In other words, it is possible to put the quantum states on other track of decay once they are on a particular route of decay. We show that one can accelerate or delay sudden death. However, there is a critical time such that if local actions are taken before that critical time then sudden death can be delayed to infinity. Any local unitary action taken after that critical time can only accelerate or delay sudden death. In finite-temparature reservoirs, we demonstrate that a whole class of entangled states exhibit sudden death. This conclusion is valid if at least one of the reservoirs is at finite-temperature. However, we show that we can still hasten or delay sudden death by local unitary transformations up to some finite time. We also study sudden death for qubit-qutrit systems. Similar to qubit-qubit systems, some states exhibit sudden death while others do not. However, the process of disentanglement can be effected due to existence of quantum interference between excited levels of qutrit. We show that it is possible to hasten, delay, or avoid sudden death by local unitary actions taken later in time.This thesis is a theoretical study of entanglement dynamics and its control of qubit-qubit and qubit-qutrit systems. In particular, we focus on the decay of entanglement of quantum states interacting with dissipative environments. Qubit-qubit entanglement may vanish suddenly while interacting with statistically independent vacuum reservoirs. Such finite-time disentanglement is called sudden death of entanglement(ESD). We investigate entanglement sudden death of qubit-qubit and qubit-qutrit systems interacting with statistically independent reservoirs at zero- and finite-temperature. It is shown that for zero-temperature reservoirs, some entangled states exhibit sudden death while others lose their entanglement only after infinite time. Thus, there are two possible routes of entanglement decay, namely sudden death and asymptotic decay. We demonstrate that starting with an initial condition which leads to finite-time disentanglement, we can alter the future course of entanglement by local unitary actions. In other words, it is possible to put the quantum states on other track of decay once they are on a particular route of decay. We show that one can accelerate or delay sudden death. However, there is a critical time such that if local actions are taken before that critical time then sudden death can be delayed to infinity. Any local unitary action taken after that critical time can only accelerate or delay sudden death. In finite-temparature reservoirs, we demonstrate that a whole class of entangled states exhibit sudden death. This conclusion is valid if at least one of the reservoirs is at finite-temperature. However, we show that we can still hasten or delay sudden death by local unitary transformations up to some finite time. We also study sudden death for qubit-qutrit systems. Similar to qubit-qubit systems, some states exhibit sudden death while others do not. However, the process of disentanglement can be effected due to existence of quantum interference between excited levels of qutrit. We show that it is possible to hasten, delay, or avoid sudden death by local unitary actions taken later in time.

Jan 1, 20091 citation

^{2}

centrifugal barrier that prevents the Rydberg electron in high-\textit{l} states from penetrating inside of the ion core, the electron is essentially uncoupled from the ion core, and the system becomes atom-like with long lifetimes, an ""almost good"" \textit{l} quantum number, and electronic transitions that follow

\Delta

^{+}

=0 and

\Delta

^{+}

=0 propensity rules. However, in most molecules access to these states, via a sequence of

\Delta

\textit{l}=+1 transitions from low-n*, low-\textit{l} states, is blocked by the necessity to traverse the ""zone of death,"" in which nonradiative decay mechanisms are prohibitively fast. We exploit Chirped Pulse millimeter-Wave (CPmmW) spectroscopy to efficiently excite Ca atoms and BaF molecules to core nonpenetrating states in the absence of nonradiative decay mechanisms. A universal method for preparing core nonpenetrating Rydberg states of molecules, which combines CPmmW spectroscopy with STImulated Raman Adiabatic Passage (STIRAP), will be discussed."