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Lund reports on atomic physics

Spin Coherence Excitation in Pr3+ :Y2SiO5

Fredrik Vestin

Published Jan 1, 2003• 0 citations
OpenAlex

Abstract

This master's thesis investigates the ground state hyperfine levels coherence time in Pr3+:Y2Si05• This property is important for the future development of quantum computers based on this or similar crystals.A suitable method to measure the coherence time at liquid helium temperature for two hyperfine levels in the 4 H3 level of Pr3+ was developed and the coherence time has also been determined approximately to 540 J.l-S.Examensarbetet undersoker koherenstiden for tva hyperfin nivaer i grundtillstandet for Pr3+:Y2Si05 .Detta ar en egenskap som ar viktig for en framtida kvantdator baserad pa denna eller liknande kristaller.En metod att mata koherenstiden vid flytande helium temperatur for tva av hyperfinnivaerna i grundtillstandet for Pr3+ har utvecklats och koherenstiden har med denna metod matts upp till 540 J.l-S.

Related papers

Magnetic Field Dependence of Optical Coherence Times in Quantum Computer Hardware Based on Pr3+:Y2SiO5

Magnus Trägårdh

This thesis investigates how the coherence time of the 3H4 – 1D2 transition of praseodymium doped into a YSO crystal is affected by an externally applied magnetic field. Such crystals, kept at or below helium temperature, are con-sidered for use as hardware in a future quantum computer, and the coherence time is one important factor affecting the error rate of gate operations in this computer. If the coherence time could be increased by magnetic fields, it could increase the fidelity of gate operations, bringing it closer to values where quan-tum computing becomes viable. The measurements were made using two-pulse photon echoes, and the measured coherence times were determined to approximately 60 µs, which corresponds to a homogeneous linewidth of 5 kHz. The coherence times showed no clear magnetic field dependence and were substantially shorter that previously reported. It could not be determined whether this was the result of unforeseen processes destroying the coherence or due to an experimental artifact.

Lund reports on atomic physics•Jan 1, 2006•0 citations

Measurement of the ground-state hyperfine coherence time of ^151Eu^3+:Y_2SiO_5

A. L. Alexander, Jevon J. Longdell, Matthew J. Sellars

We report on Raman echo measurements of the 151Eu3+Y2SiO5 ground-state hyperfine transition. Using Raman echoes in zero magnetic field the ground-state hyperfine coherence time was observed to be (15.5±2) ms. When an external magnetic field was applied, the dephasing time of the hyperfine transition was observed to decay nonexponentially, with a decay rate of (36±4) ms. This nonexponential decay is indicative of the presence of spectral diffusion, similar to that observed in Pr3+:Y2SiO5. This work indicates that under favorable conditions we can expect hyperfine coherence times longer than the value of 30 s recently reported in Pr3+Y2SiO5.

Journal of the Optical Society of America B•Aug 30, 2007•37 citations

Transient Spectral Hole-Burning in Pr : Y2SiO5

Marito Olsson-Forsberg

This work presents the methods and results of an attempt to measure the oscillator strengths in Pr3+ : Y2Si05 .Pr3+ : Y2Si05 is a promising material in current efforts to create a quantum computer.The property which is to be exploited in the quantum computing scheme proposed by the group within which this work was done, is spinpolarization.To be able to create a polarization of the nuclear spins of the Pr3+ -ions, information about the oscillator strengths of the candidate material is crucial.This is the main object of the work in this report.

Lund reports on atomic physics•Jan 1, 2003•0 citations

Development of Persistent Quantum Memories

Manjin Zhong

This thesis investigates the coherence properties of the hyperfine transitions of the 151Eu3+ ions in Eu3+:Y2SiO5 and evaluates the potential of developing quantum memories using these transitions. Quantum memories for light with long storage times are required for quantum commu- nication applications. For these memories to be useful they need to have storage times long compared to the transmission times across the communication network. For a global optical communication network this requires storage time longer than 100 ms. Rare-earth doped crystals have been identified as a suitable storage material. The storage time of these systems is limited by the coherence time of the hyperfine transitions of the optically active rare-earth ions. In previous work it had been demonstrated that coherence times as long as 1.4 seconds could be achieved for hyperfine transitions in Pr3+:Y2SiO5 by ap- plying a particular magnetic field such that the first order Zeeman shift of the transition nulled. This technique is known as zero first-order Zeeman (ZEFOZ). Due to the relatively large second order Zeeman efficient of the transitions in Pr3+:Y2SiO5, an extension of the coherence time, significantly beyond the 1.4 second mark using ZEFOZ, is not expected. However, it has been predicted that coherence times more than two orders of magnitude longer could be achieved in Eu3+:Y2SiO5 due to the smaller second order Zeeman shifts associated with the relevant hyperfine transitions. The dominant decoherence mechanism for the hyperfine transitions in diluted Eu3+:Y2SiO5 is the magnetic field perturbations caused by the random spin reconfigu- ration of the Y3+ ions in the host. By applying the ZEFOZ technique, previously used in Pr3+:Y2SiO5, the sensitivity of the transition’s frequency to environmental magnetic field perturbations was significantly reduced. Further, this strong ZEFOZ magnetic field was also shown to induce a frozen core around the Eu3+ ion, which resulted in a signifi- cant suppression of the reconfiguration of the nearby Y3+ spins. The combined effect of the reduced sensitivity and frozen core effect allowed a decoherence rate of 8 × 10−5 s−1 over 100 milliseconds to be demonstrated. The observed decoherence rate is at least an order of magnitude lower than that of any other system suitable for an optical quantum memory. Furthermore, by employing dynamic decoherence control, a coherence time of 370 ± 60 minutes was achieved. This 6 hour coherence time observed here opens up the possibility of distributing quantum entanglement via the physical transport of memories as an alternative to optical communications. It was found that even at the critical point alignment the observed coherence times showed that the Y3+ spin flips remain the dominant decoherence mechanism. To aid in the development of future strategies to further extend the coherence time beyond 6 hours, a study of the Y3+ spin dynamics in the frozen core was conducted. Four of the Y3+ sites were resolved and a complete mapping of all frozen-core Y3+ sites was limited by the inhomogeneity of the applied magnetic field. The Rabi frequency, the coherence time and lifetime as well as the interaction strength with the Eu3+ ion of one of these Y3+ ions were measured. The observed lifetime of the Y3+ ion is 27 s, which is four orders of magnitude longer than the low field value. With the technique developed, a detailed understanding of the frozen-core dynamics is possible, which would allow an extension of the hyperfine coherence time of the Eu3+ ion towards the lifetime limit. In summary, this thesis provides a detailed characterisation of the decoherence mecha- nisms of the hyperfine transitions in Eu3+:Y2SiO5. The potential of using rare-earth doped crystals for the long-term storage of quantum information with applications to long-range quantum communications is identified. The demonstrated long coherence time of the quantum transitions for information storage allows a new way of entanglement distribu- tion: entanglement is transported by physically transporting the memory crystal rather than the light. This approach opens a new regime for both quantum communication and fundamental tests of quantum mechanics.

•Jan 1, 2017•3 citations

Experimental observation of electromagnetically induced transparency in Pr3+:LaF3

Ахмеджанов Ринат Абдулхаевич, Lev Gushin, Elena Kuznetsova +3 more

We report an experimental observation of electromagnetically induced transparency (EIT) in Pr3+:LaF3 at liquid helium temperature at the 3H4(0)–1D2 (16 872 cm−1) transition. Transparency resonance at ground state hyperfine sublevels (in a Λ scheme) and a dispersion-shaped resonance due to excited state hyperfine coherences (in a V scheme) are detected. Theoretical analysis taking into account the six-level Pr3+ level structure gives qualitative agreement with the experiment.

Journal of Modern Optics•Oct 25, 2006•7 citations

Electromagnetically induced transparency and retrieval of light pulses in a Λ-type and a V-type level scheme in Pr3+:Y2SiO5

Fabian Beil, Jens Klein, Gor Nikoghosyan +1 more

We examine electromagnetically induced transparency (EIT), the optical preparation of persistent nuclear spin coherences and the retrieval of light pulses both in a Λ-type and a V-type coupling scheme in a Pr 3+ :Y 2 SiO 5 crystal, cooled to cryogenic temperatures. The medium is prepared by optical pumping and spectral hole burning, creating a spectrally isolated Λ-type and a V-type system within the inhomogeneous bandwidth of the 3 H 4 ↔ 1 D 2 transition of the Pr 3+ ions. By EIT, in the Λ-type scheme we drive a nuclear spin coherence between the ground-state hyperfine levels, while in the V-type scheme we drive a coherence between the excited-state hyperfine levels. We observe the cancellation of absorption due to EIT and the retrieval of light pulses in both level schemes. This also permits the determination of dephasing times of the nuclear spin coherence, either in the ground state or the optically excited state.

Journal of Physics B Atomic Molecular and Optical Physics•Mar 26, 2008•66 citations
This master's thesis investigates the ground state hyperfine levels coherence time in Pr3+:Y2Si05• This property is important for the future development of quantum computers based on this or similar crystals.A suitable method to measure the coherence time at liquid helium temperature for two hyperfine levels in the 4 H3 level of Pr3+ was developed and the coherence time has also been determined approximately to 540 J.l-S.Examensarbetet undersoker koherenstiden for tva hyperfin nivaer i grundtillstandet for Pr3+:Y2Si05 .Detta ar en egenskap som ar viktig for en framtida kvantdator baserad pa denna eller liknande kristaller.En metod att mata koherenstiden vid flytande helium temperatur for tva av hyperfinnivaerna i grundtillstandet for Pr3+ har utvecklats och koherenstiden har med denna metod matts upp till 540 J.l-S.
This thesis investigates how the coherence time of the 3H4 – 1D2 transition of praseodymium doped into a YSO crystal is affected by an externally applied magnetic field. Such crystals, kept at or below helium temperature, are con-sidered for use as hardware in a future quantum computer, and the coherence time is one important factor affecting the error rate of gate operations in this computer. If the coherence time could be increased by magnetic fields, it could increase the fidelity of gate operations, bringing it closer to values where quan-tum computing becomes viable. The measurements were made using two-pulse photon echoes, and the measured coherence times were determined to approximately 60 µs, which corresponds to a homogeneous linewidth of 5 kHz. The coherence times showed no clear magnetic field dependence and were substantially shorter that previously reported. It could not be determined whether this was the result of unforeseen processes destroying the coherence or due to an experimental artifact.
We report on Raman echo measurements of the 151Eu3+Y2SiO5 ground-state hyperfine transition. Using Raman echoes in zero magnetic field the ground-state hyperfine coherence time was observed to be (15.5±2) ms. When an external magnetic field was applied, the dephasing time of the hyperfine transition was observed to decay nonexponentially, with a decay rate of (36±4) ms. This nonexponential decay is indicative of the presence of spectral diffusion, similar to that observed in Pr3+:Y2SiO5. This work indicates that under favorable conditions we can expect hyperfine coherence times longer than the value of 30 s recently reported in Pr3+Y2SiO5.
This work presents the methods and results of an attempt to measure the oscillator strengths in Pr3+ : Y2Si05 .Pr3+ : Y2Si05 is a promising material in current efforts to create a quantum computer.The property which is to be exploited in the quantum computing scheme proposed by the group within which this work was done, is spinpolarization.To be able to create a polarization of the nuclear spins of the Pr3+ -ions, information about the oscillator strengths of the candidate material is crucial.This is the main object of the work in this report.
This thesis investigates the coherence properties of the hyperfine transitions of the 151Eu3+ ions in Eu3+:Y2SiO5 and evaluates the potential of developing quantum memories using these transitions. Quantum memories for light with long storage times are required for quantum commu- nication applications. For these memories to be useful they need to have storage times long compared to the transmission times across the communication network. For a global optical communication network this requires storage time longer than 100 ms. Rare-earth doped crystals have been identified as a suitable storage material. The storage time of these systems is limited by the coherence time of the hyperfine transitions of the optically active rare-earth ions. In previous work it had been demonstrated that coherence times as long as 1.4 seconds could be achieved for hyperfine transitions in Pr3+:Y2SiO5 by ap- plying a particular magnetic field such that the first order Zeeman shift of the transition nulled. This technique is known as zero first-order Zeeman (ZEFOZ). Due to the relatively large second order Zeeman efficient of the transitions in Pr3+:Y2SiO5, an extension of the coherence time, significantly beyond the 1.4 second mark using ZEFOZ, is not expected. However, it has been predicted that coherence times more than two orders of magnitude longer could be achieved in Eu3+:Y2SiO5 due to the smaller second order Zeeman shifts associated with the relevant hyperfine transitions. The dominant decoherence mechanism for the hyperfine transitions in diluted Eu3+:Y2SiO5 is the magnetic field perturbations caused by the random spin reconfigu- ration of the Y3+ ions in the host. By applying the ZEFOZ technique, previously used in Pr3+:Y2SiO5, the sensitivity of the transition’s frequency to environmental magnetic field perturbations was significantly reduced. Further, this strong ZEFOZ magnetic field was also shown to induce a frozen core around the Eu3+ ion, which resulted in a signifi- cant suppression of the reconfiguration of the nearby Y3+ spins. The combined effect of the reduced sensitivity and frozen core effect allowed a decoherence rate of 8 × 10−5 s−1 over 100 milliseconds to be demonstrated. The observed decoherence rate is at least an order of magnitude lower than that of any other system suitable for an optical quantum memory. Furthermore, by employing dynamic decoherence control, a coherence time of 370 ± 60 minutes was achieved. This 6 hour coherence time observed here opens up the possibility of distributing quantum entanglement via the physical transport of memories as an alternative to optical communications. It was found that even at the critical point alignment the observed coherence times showed that the Y3+ spin flips remain the dominant decoherence mechanism. To aid in the development of future strategies to further extend the coherence time beyond 6 hours, a study of the Y3+ spin dynamics in the frozen core was conducted. Four of the Y3+ sites were resolved and a complete mapping of all frozen-core Y3+ sites was limited by the inhomogeneity of the applied magnetic field. The Rabi frequency, the coherence time and lifetime as well as the interaction strength with the Eu3+ ion of one of these Y3+ ions were measured. The observed lifetime of the Y3+ ion is 27 s, which is four orders of magnitude longer than the low field value. With the technique developed, a detailed understanding of the frozen-core dynamics is possible, which would allow an extension of the hyperfine coherence time of the Eu3+ ion towards the lifetime limit. In summary, this thesis provides a detailed characterisation of the decoherence mecha- nisms of the hyperfine transitions in Eu3+:Y2SiO5. The potential of using rare-earth doped crystals for the long-term storage of quantum information with applications to long-range quantum communications is identified. The demonstrated long coherence time of the quantum transitions for information storage allows a new way of entanglement distribu- tion: entanglement is transported by physically transporting the memory crystal rather than the light. This approach opens a new regime for both quantum communication and fundamental tests of quantum mechanics.
We examine electromagnetically induced transparency (EIT), the optical preparation of persistent nuclear spin coherences and the retrieval of light pulses both in a Λ-type and a V-type coupling scheme in a Pr 3+ :Y 2 SiO 5 crystal, cooled to cryogenic temperatures. The medium is prepared by optical pumping and spectral hole burning, creating a spectrally isolated Λ-type and a V-type system within the inhomogeneous bandwidth of the 3 H 4 ↔ 1 D 2 transition of the Pr 3+ ions. By EIT, in the Λ-type scheme we drive a nuclear spin coherence between the ground-state hyperfine levels, while in the V-type scheme we drive a coherence between the excited-state hyperfine levels. We observe the cancellation of absorption due to EIT and the retrieval of light pulses in both level schemes. This also permits the determination of dephasing times of the nuclear spin coherence, either in the ground state or the optically excited state.