# Quantum Structure for Modelling Emotion Space of Robots
## 5 Concluding remarks  
The immense power of quantum computation (QC) is exploited to model quantum structure for expression of robot emotions. The proposed quantum emotion space (QES) uses three entangled qubit sequences to store the emotion in a three-dimensional space that consists of a pleasure-arousal (PA) plane and a time axis. This mechanism provides a technique to represent and manipulate a robot's emotion space, wherein the process of initialisation and transition, which are essential in any manipulation of emotions using the QES, can be realised (using the Identity, Hadamard, and CNOT gates). Based on this, a unitary matrix can be used to track and reverse changes to a robot's emotions. Finally, the intricacies of the quantum measurement operations employed for emotion retrieval in QES were presented and discussed.  
To improve the proposed framework, in future and ongoing work, the results emanating from this study will be extended in the following directions. First, the emotion transition matrix, which is essential for tracking changes in a robot's emotional state, needs further rigorous study because, in practical cases, the stimuli that influences the changes in emotional states are induced by many factors [25]. Consequently, the emotion transition matrix should be robust enough to model these different cause-effect mechanisms. Second, the 16 common sorts of robot's emotions that are mapped in the QPA plane are defined by modifying the traditional PA plane. To satisfy the emotional computation of robots under different circumstance (e.g., expectations from the humanoid robot behaviour [26; 27]), those emotions might require additional refinement. Third, the use of quantum space of robot emotion to construct a harmonious and natural interface for human-robot interaction should be explored. This will support the use of robots to understand, adapt, and respond to human mood swings as well as other applications in emotional intelligence [28]. Fourth, superposition and entanglement are two fundamental properties of quantum information, it is important that the full benefits of these properties are exploited in modelling the control, planning and reasoning, etc. envisaged in future robots and their interaction with the environment. This will entail necessary modifications to the QES to facilitate definition of more subtle emotions or accelerate the emotional computing tasks. Fifth, the need to adjust the present layout of the QES, including its mathematical groundwork, as required for advanced applications, such as the use of qubots and their integration in user-emotion detection systems for social robots [29] deserve attention. Sixth, noise in quantum gates will limit the size of quantum circuits that can be executed reliably [30]. To realise the QES in a more realistic scenario, the study of quantum error correction is essential in achieving fault-tolerant QC that can deal not only with noise in stored quantum information but with faults in quantum gates, preparation, and measurements. In concluding, we reiterate that while the distance down the road to full scale deployment of quantum computation in robotics is a long one, like many others before it, the formulation of our proposed QES provides a decisive first step in that exploration.  
Conceptualization, F.Y., A.M.I., and S.J.; methodology, F.Y., A.M.I.; writing-original draft preparation, F.Y., S.J., and A.M.I.; writing-review and editing, F.Y. and A.M.I.; supervision, H.Y.; project administration, A.M.I.; funding acquisition, A.M.I.  
This study is sponsored, in full, by the Prince Sattam Bin Abdulaziz University, Saudi Arabia via the Deanship for Scientific Research funding granted to the ACIIS Research group project number 2019/01/9862.  
The authors declare no conflict of interest.