Proposal and proof-of-principle demonstration of non-destructive detection of photonic qubits using a Tm:LiNbO3 waveguide

Abstract

Non-destructive detection of photonic qubits is an enabling technology for quantum information processing and quantum communication. For practical applications, such as quantum repeaters and networks, it is desirable to implement such detection in a way that allows some form of multiplexing as well as easy integration with other components such as solid-state quantum memories. Here, we propose an approach to non-destructive photonic qubit detection that promises to have all the mentioned features. Mediated by an impurity-doped crystal, a signal photon in an arbitrary time-bin qubit state modulates the phase of an intense probe pulse that is stored during the interaction. Using a thulium-doped waveguide in LiNbO3, we perform a proof-of-principle experiment with macroscopic signal pulses, demonstrating the expected cross-phase modulation as well as the ability to preserve the coherence between temporal modes. Our findings open the path to a new key component of quantum photonics based on rare-earth-ion-doped crystals.

Properties of a Rare-Earth-Ion-Doped Waveguide at Sub-Kelvin Temperatures for Quantum Signal Processing

“…Moreover, the measured properties match those observed using Tm 3+ :LiNbO 3 bulk crystals under similar conditions [24], and improve upon those observed with other REIdoped waveguides [20][21][22]. In addition, our measurements establish a ratio of coherence lifetime to ( 3 H 4 ) excited-state population lifetime that is greater than one [18,25], which benefits applications in the field of cavity quantum electrodynamics [26] or employing crossphase modulation [12]. To show key requirements for efficient quantum information processing, we burn persistent holes to transparency, and tailor a 0.5 GHzbandwidth atomic frequency comb (AFC) [15,16] with a finesse of three on a vanishing absorption background using magnetic fields up to 20 kG.…”

“…However, work employing REI-doped crystalline waveguides has, until only the past year, been restricted to LiNbO 3 -generally doped with thulium -into which waveguides were fabricated by means of titanium indiffusion [3,5,9,12,17]. A likely explanation for the lack of investigations using other REIs in Ti 4+ :LiNbO 3 is that an earlier low-temperature characterization of -all of which guide light in unperturbed regions of the REI-doped crystal.…”

“…using frequency shifts or on-demand quantum memories, could pave the way to the development of a practical quantum repeater [9,11,12]. A promising avenue to this end, and to quantum information processing in general, is based on qubit interfaces using rare-earth-ion-doped (REI-doped) crystals at cryogenic temperatures [3,5,[12][13][14][15][16]. Consequently, the development of rare-earth-ion-doped waveguides constitutes an exciting and important path towards applications.…”

Nondestructive photon detection using a single rare-earth ion coupled to a photonic cavity

“…Rare-earth-doped crystals have been successfully used for optical quantum memories [12][13][14] and have been suggested for scalable quantum computing [15]. A scheme for performing nondestructive measurements utilizing an ensemble of rare-earth ions coupled to a bulk crystalline waveguide has recently been suggested [16]. It is also now possible to observe single rare-earth ions in bulk crystal [17][18][19][20][21] and to map between ion spins and a photon's polarization [22].…”

“…Normally, detecting a photon necessitates its destruction. With an unheralded time-bin qubit, a nondestructive photon measurement can be made on both bins in order to know if there is a photon in one without destroying the qubit [16]. With a heralded time-bin photon, we could entangle the REI with the time-bin qubit by limiting our quantum nondemolition measurement to one of the time bins.…”