اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدLong-lived driven solid-state quantum memory
120
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We investigate the performance of inhomogeneously broadened spin ensembles as quantum memories under continuous dynamical decoupling. The role of the continuous driving field is two-fold: first, it decouples individual spins from magnetic noise; second and more important, it suppresses and reshapes the spectral inhomogeneity of spin ensembles. We show that a continuous driving field, which itself may also be inhomogeneous over the ensemble, can enhance the decay of the tails of the inhomogeneous broadening distribution considerably. This fact enables a spin ensemble based quantum memory to exploit the effect of cavity protection and achieve a much longer storage time. In particular, for a spin ensemble with a Lorentzian spectral distribution, our calculations demonstrate that continuous dynamical decoupling has the potential to improve its storage time by orders of magnitude for the state-of-art experimental parameters.
قيم البحث
اقرأ أيضاً
We argue that long optical storage times are required to establish entanglement at high rates over large distances using memory-based quantum repeaters. Triggered by this conclusion, we investigate the $^3$H$_6$ $leftrightarrow$ $^3$H$_4$ transition
at 795.325 nm of Tm:Y$_3$Ga$_5$O$_{12}$ (Tm:YGG). Most importantly, we show that the optical coherence time can reach 1.1 ms, and, using laser pulses, we demonstrate optical storage based on the atomic frequency comb protocol up to 100 $mu$s as well as a memory decay time T$_M$ of 13.1 $mu$s. Possibilities of how to narrow the gap between the measured value of T$_m$ and its maximum of 275 $mu$s are discussed. In addition, we demonstrate quantum state storage using members of non-classical photon pairs. Our results show the potential of Tm:YGG for creating quantum memories with long optical storage times, and open the path to building extended quantum networks.
We demonstrate long-lived coherence in internal hyperfine states of a single Ca{43} trapped-ion qubit $[T_2=1.2(2)s]$, and in external motional states of a single Ca{40} trapped-ion qubit $[T_2=0.18(4)s]$, in the same apparatus. The motional decohere
nce rate is consistent with the heating rate, which was measured to be 3(1) quanta/sec. Long coherence times in the external motional states are essential for performing high-fidelity quantum logic gates between trapped-ion qubits. The internal-state $T_2$ time that we observe in Ca{43}, which has not previously been used as a trapped-ion qubit, is about one thousand times longer than that of physical qubits based on Ca{40} ions. Using a single spin-echo pulse to ``re-phase the internal state, we can detect no decoherence after 1s, implying an effective coherence time $T_2^{mbox{tiny SE}} gtish 45s$. This compares with timescales in this trap for single-qubit operations of ish 1us, and for two-qubit operations of ish 10us.
We investigate theoretically the coupling of a cavity mode to a continuous distribution of emitters. We discuss the influence of the emitters inhomogeneous broadening on the existence and on the coherence properties of the polaritonic peaks. We find
that their coherence depends crucially on the shape of the distribution and not only on its width. Under certain conditions the coupling to the cavity protects the polaritonic states from inhomogeneous broadening, resulting in a longer storage time for a quantum memory based on emitters ensembles. When two different ensembles of emitters are coupled to the resonator, they support a peculiar collective dark state, also very attractive for the storage of quantum information.
The transfer of information between different physical forms is a central theme in communication and computation, for example between processing entities and memory. Nowhere is this more crucial than in quantum computation, where great effort must be
taken to protect the integrity of a fragile quantum bit. Nuclear spins are known to benefit from long coherence times compared to electron spins, but are slow to manipulate and suffer from weak thermal polarisation. A powerful model for quantum computation is thus one in which electron spins are used for processing and readout while nuclear spins are used for storage. Here we demonstrate the coherent transfer of a superposition state in an electron spin processing qubit to a nuclear spin memory qubit, using a combination of microwave and radiofrequency pulses applied to 31P donors in an isotopically pure 28Si crystal. The electron spin state can be stored in the nuclear spin on a timescale that is long compared with the electron decoherence time and then coherently transferred back to the electron spin, thus demonstrating the 31P nuclear spin as a solid-state quantum memory. The overall store/readout fidelity is about 90%, attributed to systematic imperfections in radiofrequency pulses which can be improved through the use of composite pulses. We apply dynamic decoupling to protect the nuclear spin quantum memory element from sources of decoherence. The coherence lifetime of the quantum memory element is found to exceed one second at 5.5K.
We investigate a hybrid quantum circuit where ensembles of cold polar molecules serve as long-lived quantum memories and optical interfaces for solid state quantum processors. The quantum memory realized by collective spin states (ensemble qubit) is
coupled to a high-Q stripline cavity via microwave Raman processes. We show that for convenient trap-surface distances of a few $mu$m, strong coupling between the cavity and ensemble qubit can be achieved. We discuss basic quantum information protocols, including a swap from the cavity photon bus to the molecular quantum memory, and a deterministic two qubit gate. Finally, we investigate coherence properties of molecular ensemble quantum bits.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
