Spatial-mode Degrees Of Freedom Research Articles

A novel quantum dialogue without information leakage based on single photons in both polarization and spatial-mode degrees of freedom

This paper puts forward a novel quantum dialogue (QD) protocol without information leakage based on single photons in both polarization and spatial-mode degrees of freedom. In this protocol, the receiver sends his private message to the sender in the way of quantum secure direct communication; and the receiver decodes out the private message of the sender with the help of auxiliary single photons in two degrees of freedom, double controlled-not (CNOT) operations and an auxiliary classical bit sequence sent from the sender. As a result, no information leakage takes place. Moreover, this protocol is proven to defeat the intercept-resend attack, the measure-resend attack, the entangle-measure attack and the Trojan horse attack from an outside eavesdropper. This protocol only employs single photons in two degrees of freedom as quantum resource and needs single-photon measurements. The qubit efficiency of this protocol is as high as 66.7%.

Bidirectional remote hyperstate preparation under common quantum control using hyperentanglement

In this paper, we propose a new, to the best of our knowledge, protocol that enables two distant parties to prepare a photon hyperstate for each other encoded at the same time in both polarization and spatial-mode degrees of freedom. The bidirectional remote hyperstate preparation is demanded so that it is remotely controllable by a common supervisor. Such a task appears possible using a shared quantum channel made of five photons entangled simultaneously in the two corresponding degrees of freedom, the so-called hyperentanglement. We first design a near-deterministic scheme to produce a relevant five-photon hyperentanagled state to be served as the working nonlocal channel and then present our protocol for controlled bidirectional remote hyperstate preparation, which always is successful.

High-capacity quantum key distribution based on hyperentangled Bell states and hyper-encoding

According to the properties of the hyperentangled Bell state and hyper-encoding technology, this paper proposes a high-capacity quantum key distribution protocol with qudits hyper-encoded in polarization and spatial mode degrees of freedom (DOFs). In our protocol, 8 bits of information can be transmitted in one iteration. In contrast, the previous quantum key distribution protocols can only transmit up to 4 or 6 bits in one iteration. Moreover, quantum memory is unnecessary in our protocol. We analyze the relationship between the amount of eavesdropping and the success rate of eavesdropping. With the increase of eavesdropping information, the eavesdropping success probability will decrease sharply. The results show that our protocol is secure. Finally, this protocol is flexible; each qubit has two completely independent DOFs. If one DOF is destroyed, the other can still be used to transmit secure information. The protocol may be useful in the future quantum communication field.

Practical multipartite entanglement distribution in noisy channels

Entanglement among multiple parties is vital for practical quantum information applications. As two kinds of typical multipartite entangled state, the W and Greenberger-Horne-Zeilinger (GHZ) states have attracted a lot of attention. In this paper, we propose two practical linear optical schemes for multipartite entanglement distribution in noisy channels. Using the time-bin or spatial-mode degree of freedom (DoF) encoding, the influence of the noise will be eliminated and perfect W or GHZ state can be achieved among different nodes in a deterministic way. Moreover, we construct quantum circuits, which can be implemented with current technology. These results contribute to long-distance quantum communication both in theoretical and experimental points of view.

Error-detected three-photon hyperparallel Toffoli gate with state-selective reflection

We present an error-detected hyperparallel Toffoli (hyper-Toffoli) gate for a three-photon system based on the interface between polarized photon and cavity-nitrogen-vacancy(NV) center system. This hyper-Toffoli gate can be used to perform double Toffoli gate operations simultaneously on both the polarization and spatial-mode degrees of freedom (DoFs) of a three-photon system with a low decoherence, shorten operation time, and less quantum resources required, in compared with those on two independent three-photon systems in one DoF only. As the imperfect cavity-NV-center interactions are transformed into the detectable failures rather than infidelity based on the heralding mechanism of detectors, a near-unit fidelity of the quantum hyper-Toffoli gate can be implemented. By recycling the procedures, the efficiency of our protocol for the hyper-Toffoli gate is improved further. Meanwhile, the evaluation of gate performance with achieved experiment parameters shows that it is feasible with current experimental technology and provides a promising building block for quantum compute.

Improvement of information leakage resistant quantum dialogue with single photons in both polarization and spatial-mode degrees of freedom

Improvement of information leakage resistant quantum dialogue with single photons in both polarization and spatial-mode degrees of freedom

Joint remote preparation of a single-photon hyper-state with two pairs of hyper-Bell states

Hyper-entanglement is gaining more and more attentions thanks to its outstanding applications in processing quantum information. It is considered as a quantum resource in many important tasks. In this work, we deal with a tripartite task for three remote parties Alice, Bob and Charlie. Namely, Alice and Bob are two senders who independently share the full information of an arbitrary single-photon state which is encoded simultaneously in two different degrees of freedom, the spatial-mode degree of freedom and the polarization degree of freedom (hereafter called photon’s hyper-state). We show that Alice and Bob can jointly prepare for the receiver Charlie such a hyper-state of the photon when they share beforehand two pairs of hyper-Bell states.

Efficient semiquantum key distribution based on single photons in both polarization and spatial-mode degrees of freedom

In this paper, we propose an efficient semiquantum key distribution (SQKD) protocol which is based on single photons in both polarization and spatial-mode degrees of freedom. This protocol is feasible for a quantum communicant distributing a random private key to a classical communicant. This protocol needn't require the classical communicant to use any quantum memory or unitary operation equipment. We validate the complete robustness of the transmissions of single photons between two communicants. It turns out that during these transmissions, if Eve wants not to be detected by two communicants, she will obtain nothing useful about the final shared key bits. Compared with Boyer et al.'s famous pioneering SQKD protocol (Phys Rev Lett, 2007, 99:140501), this protocol has double quantum communication capacity, as one single photon with two degrees of freedom for generating the key bits can carry two private bits; and this protocol has higher quantum communication efficiency, as it consumes less qubits for establishing a private key of the same length. Compared with the only existing SQKD protocol with single photons in two degrees of freedom (Int J Theor Phys, 2020, 59: 2807), this protocol has higher quantum communication efficiency.

One-step quantum secure direct communication

Quantum secure direct communication (QSDC) attracts much attention for it can transmit secret messages directly without sharing a key. In this article, we propose a one-step QSDC protocol, which only requires to distribute polarization-spatial-mode hyperentanglement for one round. In this QSDC protocol, the eavesdropper cannot obtain any message, so that this protocol is unconditionally secure in principle. This protocol is a two-way quantum communication and has high capacity for it can transmit two bits of secret messages with one pair of hyperentanglement. With entanglement fidelities of both polarization and spatial-mode degrees of freedom being 0.98, the maximal communication distance of this one-step QSDC can reach about 216 km. QSDC can also be used to generate the key. In this regard, the key generation rate is estimated about 2.5 times of that in the entanglement-based QKD with the communication distance of 150 km. With the help of future quantum repeaters, this QSDC protocol can provide unconditionally secure communication over arbitrarily long distance.

Quantum dialogue based on quantum encryption with single photons in both polarization and spatial-modedegrees of freedom

<p indent=0mm>In this paper, a novel information-leakage-resistant quantum dialogue (QD) protocol with single photons in both polarization and spatial-mode degrees of freedom is proposed. This protocol utilizes quantum encryption technology to overcome the information leakage problem; the protocol utilizes quantum encryption and decoy photon technologies to dually protect the single photons with two degrees of freedom used for encoding two communicants’ private classical bits, and makes the initial states of the single photons with two degrees of freedom for encoding shared between two communicants through quantum key encryption and decryption. The information-theoretical efficiency of this protocol is 40%.

Heralded high-fidelity quantum hyper-CNOT gates assisted by charged quantum dots inside single-sided optical microcavities.

Photonic hyper-parallel quantum information processing (QIP) can simplify the quantum circuit and improve the information-processing speed, as well as reduce the quantum resource consumption and suppress the photonic dissipation noise. Here, utilizing the singly charged semiconductor quantum dot (QD) inside single-sided optical microcavity as the potentially experimental platform, we propose five schemes for heralded four-qubit hyper-controlled-not (hyper-CNOT) gates, covering all cases of four-qubit hyper-CNOT gates operated on both the polarization and spatial-mode degrees of freedom (DoFs) of a two-photon system. The novel heralding mechanism improves the fidelity of each hyper-CNOT gate to unity in principle without the strict restriction of strong coupling. The adaptability and scalability of the schemes make the hyper-CNOT gates more accessible under current experimental technologies. These heralded high-fidelity photonic hyper-CNOT gates can therefore have immense utilization potentials in high-capacity quantum communication and fast quantum computing, which are of far-reaching significance for QIP.

Information leakage resistant quantum dialogue with single photons in both polarization and spatial-mode degrees of freedom

In this paper, a novel quantum dialogue (QD) protocol is proposed based on single photons in both polarization and spatial-mode degrees of freedom. In the proposed QD protocol, the initial states of single photons in both polarization and spatial-mode degrees of freedom used for encoding are privately shared between two communicants through the direct transmissions of their auxiliary counterparts from one communicant to another. As a result, the information leakage problem is avoided. Moreover, the detailed security analysis also shows that the proposed QD protocol can resist Eve's several famous active attacks, such as the Trojan horse attack, the intercept-resend attack, the measure-resend attack and the entangle-measure attack. The proposed QD protocol only needs single photons in both polarization and spatial-mode degrees of freedom as quantum resource and adopts single-photon measurements. As a result, it is feasible in practice as the preparation and the measurement of a single photon in both polarization and spatial-mode degrees of freedom can be accomplished with current experimental techniques.

Fiber Vector Eigenmode Multiplexing Based High Capacity Transmission Over 5-km FMF With Kramers-Kronig Receiver

Vector modes (VMs) with spatially nonhomogeneous polarization patterns, combining polarization and spatial-mode degrees of freedom together, are regarded as the eigenmodes of optical fiber. Such eigenmodes have potential to be used to implement the high capacity spatial division multiplexing (SDM)/mode division multiplexing (MDM) based optical fiber communication systems. Here, we respectively demonstrate 2 VMs of the same order (l = +2, EH11o and EH11e modes) and 2 VMs of different orders (l = 0, HE11o mode and l = +2, EH11e mode) multiplexing transmissions over 5-km few-mode fiber (FMF). The mode crosstalk after FMF transmission has been minimized to prepare high capacity signal transmission without multiple-input-multiple-output (MIMO) digital signal processing (DSP). To increase the transmission capacity and decrease the system cost, the Kramers-Kronig (KK) receiver has been employed and the single-wavelength two sets of eigenmodes multiplexed 360 Gbit/s and 400 Gbit/s signal transmissions over 5-km FMF link are realized, respectively. Then, to further burst the transmission capacity, 2 vector-mode-division-multiplexing channels (HE11o and EH11e modes) in combination of 5 wavelength-division-multiplexing (WDM) channels with a total of 10 parallel channels have been demonstrated. A total data rate of 1.12 Tbit/s with 28 GBaud 16-state quadrature amplitude modulation (QAM) signal has been realized over the 5-km FMF. In all data-carrying experimental demonstrations, the bit-error rate (BER) performance of each VM channel is below the 7% hard decision forward error correction threshold (FEC) at BER of 3.8 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> . The experimental results highlight that the VMDM-based optical transmission technology could find enormous potential in huge-capacity short-reach optical interconnects.

High-capacity measurement-device-independent quantum secure direct communication

As an important branch of quantum communication, quantum secure direct communication (QSDC) can directly transmit secure information between two communication parties without keys. Measurement-device-independent quantum secure direct communication (MDI–QSDC) is immune to all the attacks at detector’s side and thus can eliminate the security loopholes associated with measurement devices. Existing MDI–QSDC protocols encode secure information in only one degree of freedom (DOF) of photons. In this paper, we propose a high-capacity MDI–QSDC protocol by encoding secure information in photons’ polarization and spatial-mode DOFs. With hyper-encoding in two DOFs, we can double photons’ channel capacity and effectively increase MDI–QSDC’s communication efficiency. Moreover, for each encoded qudit, the states in two DOFs are totally independent. If a detection failure or error occurs on one DOF, the state in the other DOF can still be used to transmit secure information. This hyper-encoding MDI–QSDC may have potential applications in future quantum communication.

Free-space quantum secure direct communication based on decoherence-free space

We propose a free-space quantum secure direct communication protocol by using hyper-encoded single photons. The communication parties can securely exchange private information in a deterministic way. In this protocol, single photons are encoded simultaneously by both the polarization and spatial-mode degrees of freedom that constitute a decoherence-free space. The detrimental effect introduced by either reference-frame misalignment or practical channel rotational noise is passively suppressed. Finally, the security of our protocol against classical individual attacks is proved by quantum mutual information.

Semi-quantum key distribution protocol based on the hyperentanglement Bell state of polarization-spatial mode

The semi-quantum key distribution protocol based on the hyperentanglement Bell state of polarization-spatial mode is presented in this paper. This protocol is utilized to share the session keys and construct key hierarchy of security systems in high capacity between the legitimate users securely. Different from the previous protocols, two quantum non-demolition detectors are constructed with cross-Kerr nonlinearities and different phase shifts for distinguishing the Bell states in spatial mode degree of freedom. Meanwhile, this protocol can improve the capacity and efficiency when the legitimate users share the session keys. And the technology of the hyperentanglement purification and hyperentanglement concentration can enhance the robustness and stability of this protocol. At last, this protocol proposed in this paper can withstand several kinds of attacks.

Complete hyperentangled state analysis using weak cross-Kerr nonlinearity and auxiliary entanglement

We present a new method for the complete analysis of hyperentangled Bell state and Greenberger–Horne–Zeilinger state in polarization and spatial-mode degrees of freedom, resorting to weak cross-Kerr nonlinearity and auxiliary frequency entanglement. The weak cross-Kerr nonlinearity with small phase shift is used to construct quantum nondestructive detector, and it is realizable with the current technology. Compared with the previous schemes, our scheme largely reduces the requirement on nonlinearity with the help of auxiliary entanglement in the third degree of freedom. Our method provides an efficient avenue for the hyperentangled state analysis, and will be useful for high-capacity quantum information processing.

Semi-Quantum Key Distribution with Single Photons in both Polarization and Spatial-Mode Degrees of Freedom

In this paper, a novel semi-quantum key distribution (SQKD) protocol is designed based on single photons in both polarization and spatial-mode degrees of freedom, which allows to establish a raw key between one quantum communicant and one classical communicant. The proposed SQKD protocol only adopts one kind of quantum state as the initial quantum resource. The detailed security analysis shows that it can resist Eve's active attacks, such as the intercept-resend attack, the measure-resend attack, the Trojan horse attack and the entangle-measure attack. The proposed SQKD protocol only needs single photons in both polarization and spatial-mode degrees of freedom as quantum resource and employs single-photon measurements. Thus, it has excellent feasibility, since the preparation and the measurement of a single photon in both polarization and spatial-mode degrees of freedom can be easily acheived with present quantum technologies.

Complete hyperentangled Bell state analysis assisted by hyperentanglement

We present a simple scheme for the complete analysis of hyperentangled Bell states in polarization and spatial-mode degrees of freedom (DOFs) assisted by time-bin–frequency hyperentanglement. In previous schemes of distinguishing the 16 hyperentangled Bell states, many non-linear interaction systems are widely used to construct a quantum gate, such as cross-Kerr non-linearity, quantum-dot spin in an optical microcavity and nitrogen-vacancy centers in a resonator. In our scheme, we utilize the time-bin and frequency DOFs of a photon system as the auxiliary DOFs to analyze polarization–spatial-mode hyperentangled Bell states, and the distinguishing principle is quite different from the former schemes that use the non-linear interactions. As the manipulation of time-bin and frequency DOFs of photons is efficient and feasible with current technology, this scheme will be useful for high-capacity quantum information processing based on hyperentanglement.

Improvement of High-Capacity Three-Party Quantum Secret Sharing with Single Photons in both the Polarization and the Spatial-Mode Degrees of Freedom

Recently, Wang et al. put forward a high-capacity three-party quantum secret sharing (QSS) protocol with single photons in both the polarization and the spatial-mode degrees of freedom (Int J Theor Phys (2013) 52:1043–1051). In this paper, the communication capacity of Wang et al.’s QSS protocol is improved by providing more composite unitary operations for Alice’s encoding. Compared with Wang et al.’s QSS protocol, the improved protocol doubles the communication capacity of the photon for sharing Alice’s secret bits. The improved protocol only needs two-qubit single-photon states in both the polarization and the spatial-mode degrees of freedom and single-photon measurements. Compared with the QSS protocols based on entangled states and entangled state measurements, the improved protocol is more feasible.